//best
// USE THIS BUT BE EXTRMELY CAREFUL TO KEEP checking
//XCX IVC CCM (these are supppose to error) - this is working fine.....
//They are critical for coding.
//Currently up to line 914
// issue currently with order of notations CM XI is valid XI CM (not valid)
//but software showing both as ok - NEEDS TO BE FIXED WITH PRIORITY
//ISSUE IS ONLY WITH 2 NOTATIONS
//logic of programme alsmost complete:
// need to add total for all subtractive notations...
// then apply other rules for invalid numbers
// then the untotal will be all the other characters which have not been processed
//best
// USE THIS BUT BE EXTRMELY CAREFUL TO KEEP checking
//XCX IVC CCM (these are supppose to error)
// It also does not get to the above conditions if numeral is longer such as MIVC.. now fixed
//They are critical for coding.
//NEED TO RE-CHECK LOGIC OF HOW twoSubtractiveNotations IS SET TO true - TOTAL IS DOUBLE (WRONG)
//IVCM now fails as expected
// added code to support both directions looking in rule 3
// XCX and IVC still ok... but CCM overruns i counter to 5.. bigger than length#
// trying something like IVC to reach rule 3 ver2.... it reaches max index
// OUTSTANDING.
//CMIV - it is doubling value to 1808 instead of 909...
// this is issue of CM (i index) IV (j index) comparing to CM (j index) and IV (i index)
//Everything else is fixedg

import java.util.Scanner;
import java.util.Arrays;
/*
Online Java - IDE, Code Editor, Compiler
valu`va
Online Java is a quick and easy tool that helps you to build, compile, test your programs online.
*/
// need to address finding match of 4 consecutive numerals
// need to address errors on word document
// can not handle VII or VIII
//switching technique

public class Main
{
    public static void main(String[] args) {
    System.out.println("Welcome to Online IDE!! Happy Coding :)");
    char[] acceptedNumerals = new char[]{'M','D','C','L','X', 'V','I'};
    //These are all accepted roman numerals
    int number; //This is set once end user specifies number numerals in their number to be inputted
    boolean noMatch=true; // this flag is used to check if the numeral entered is a valid one
    int j; //used to increment the character array containing user input of numeral
    int count=0; // this keeps track number times end user has entered a character. It can be decremented if it fails validation.
    Scanner reader=null;
    // This is used to ascertain how many digits end user wants
    reader = new Scanner(System.in); // Reading from System.in
    System.out.println("Enter number numerals in the number to be converted to decimal:");
    number=reader.nextInt();
    char inputtedNumerals[] = new char[number]; // this creates character array with end user specified size
    int [][] posValues = new int [number][2]; // this is used to keep track of:
    // this is 2D array. 'number' simply increments with array index of the roman numeral in character array
    // the multidimensal aspect at 0 index will store: index of which numeral i.e M is 0, D is 1
    //aspect at 1 index will store: decimal conversion
    // This will support later analysis.
    //all values will be set to 1 to ensure a repeat conversion is not processed;
    
    do
    {
        reader = new Scanner(System.in); // Reading from System.in
        System.out.println("Enter roman numeral " + (count+1) + " of " + number + ":"); // end user prompted to enter roman numeral
        inputtedNumerals[count]=reader.next().charAt(0);
        count++;

        for (j=0; j<inputtedNumerals.length;j++) // this will check each item in the inputted area against 7 roman numerals.
        // the condition could equally be set to count for better loop efficiency if the
        //number entered is long
        {
            for (int k=0; k<acceptedNumerals.length;k++) // this goes through roman numerals
            {
                if (inputtedNumerals[j]==acceptedNumerals[k]) // this checks to see if the roman numerals entered are valid
                {
                    posValues[count-1][0]=k; // Variable k keeps a record of index of the roman numeral stored in acceptedNumerals
                    // This switch statement now checks 'k'validposition in hierarcy of the 7 numerals.
                    //'M','D','C','L','X', 'V','I'
                    // Depending on the roman numeral value, it will also store the decimal conversion into posValues array.
                    
                    switch(k)
                    {
                        case 0:
                            posValues[count-1][1]=1000;
                            break;
                        
                        case 1:
                            posValues[count-1][1]=500;
                            break;
                        
                        case 2:
                            posValues[count-1][1]=100;
                            break;
                        
                        case 3:
                            posValues[count-1][1]=50;
                            break;
                        
                        case 4:
                            posValues[count-1][1]=10;
                            break;
                        
                        case 5:
                            posValues[count-1][1]=5;
                            break;
                            
                        case 6:
                            posValues[count-1][1]=1;
                            break;
                    }
                    noMatch=false; // This sets flag stating match has been found.
                    break;
                }
            }
            
            // This will now give information if the user input is valid for each numeral.
            // If found to be incorrect, the count will go back and end user will need to enter it again.
            if (noMatch==true)
            {
                System.out.println("Please input a successful roman numeral: M D C L X V I");
                count=count-1;
                break;
            }
        }
    
    } while (count<inputtedNumerals.length); // do while loop will end once count reaches the input user for length of roman numerals.
    
    String str = String.valueOf(inputtedNumerals);
    System.out.println("This will be converted to decimal:" + str); // This informs end user of the roman numerals to be converted
    
    performConversion pc = new performConversion(acceptedNumerals, inputtedNumerals,posValues,str); // calls constructor in class to perform conversion
    }
}

class performConversion
{
    int tempA=0;
    int tempB=0;
    boolean FlagSet=false;
    int sumNotAdded=0;
    int rule4;
    boolean rule3Fail=false;
    char[] inputtedNumerals; // this contains numerals entered by end user
    char[] acceptedNumerals; // this contains array of all accepted numerals
    int [][] posValues; // this keeps track for the index for numeral and also its conversion into decimal
    int total;
    int sum;
    int consecutiveOccurrences;
    String numeralsToString;
    boolean correctOrder=false;
    int oneNumeral;
    int twoNumerals;
    boolean illegalSubtractive=false;
    boolean illegalFourInARowState=false;
    int temp1=0;
    boolean valueBeforeSubtractiveNotation=false;
    int runningTotal=0;
    boolean validNumber=false;
    // This is the constructor used to call the converter method.
    
    public performConversion (char[] aNumerals, char [] inputNumerals, int [][] pValues, String numeralsToString)
    {
        int pc[] = new int[pValues.length];
        this.acceptedNumerals=aNumerals;
        this.inputtedNumerals=inputNumerals;
        this.posValues=pValues;
        this.numeralsToString=numeralsToString;
        
        converter(pc); // this variable has been passed into the method since for some reason it did not pick up the variable even though scope was correct.
    }
    
    public void converter(int [] processedConversion)
    {
        // There will be NO issues in performing conversion of a single roman numeral
        System.out.println("the length is:" + inputtedNumerals.length);
        
        if (inputtedNumerals.length<2) // This functions correctly.
        {
            System.out.println("Conversion is single:" + posValues[0][1]);
        }
        
        // ONCE ALL PRINCIPLES ARE UNDERSTOOD FOR A VALID ROMAN NUMERAL, THE CODE WILL BE IMPLEMENTED FURTHER
        System.out.println("numerals in the roman numeral:" + posValues.length);
        int valueConsecutiveOccurences[] = new int [posValues.length];
        int indexCount=0;
        // These values can only occur once in roman numeral. A counter is kept.
        int countV=0;
        int countL=0;
        int countD=0;
        int zeroIndexCount=0; // on instances, the counter has to start from zeroindex notation
        int rule4Single=0; //this keeps a total of rule 4
        int rule5=0; // this keeps total at rule 5
        int rule5total;
        boolean rule5State=false; // state is set if rule 5 is entered
        int rule6=0; // this keeps total at rule 6
        int rule6total;
        boolean rule6State=false; // state is set if rule 6 is entered
        int rule7=0; // this keeps total at rule 7
        
        int rule7total;
        boolean rule7State=false; // state is set if rule 7 is entered
        // used for
        //Rule 4: Only I, X, and C can be used as subtractive numerals.
        //There can be 6 combinations when we subtract.
        //These are IV = 5 - 1 = 4; IX = 10 - 1 = 9; XL = 50 - 10 = 40;
        // XC = 100 - 10 = 90; CD = 500 - 100 = 400; and CM = 1000 - 100 = 900
        //Another useful IMPORTANT information found on a site is that two subtractive numerals can not be adjacent such as:
        // CDCM since CM is higher however CM CD is also invalid (range is 100-900)
        // The following is invalid: IXIV even though IV is smaller than IX. This is because they are both in same range 1-9
        // In that respect, XC XL is invalid.. both notations are 10-90
        // XCIV is ok
        //{'M','D','C','L','X', 'V','I'};
        // I have partially implemented the rule here since it is too complex.
        String IV = "IV";
        String IX = "IX";
        String XL = "XL";
        String XC = "XC";
        String CD= "CD";
        String CM= "CM";
        int threeInRow=0;
        String [] subtractiveNumerals = new String []{IV,IX,XL,XC,CD,CM};
        int [][] subtractiveNumeralsRange = new int[6][2];
        subtractiveNumeralsRange[0][0] = 1; subtractiveNumeralsRange[0][1] = 4;
        subtractiveNumeralsRange[1][0] = 1; subtractiveNumeralsRange[1][1] = 9;
        subtractiveNumeralsRange[2][0] = 10; subtractiveNumeralsRange[2][1] = 40;
        subtractiveNumeralsRange[3][0] = 10; subtractiveNumeralsRange[3][1] = 90;
        subtractiveNumeralsRange[4][0] = 100; subtractiveNumeralsRange[4][1] = 500;
        subtractiveNumeralsRange[5][0] = 100; subtractiveNumeralsRange[5][1] = 900;
        int sum1=0;
        int total1=0;
        boolean flagError=false;
        boolean result=false;
        int total2=0;
        boolean twoSubtractiveNotations=false;
        boolean singleSubtractiveNotations=false;
        boolean IplacedIncorrect=false;
        boolean rule2State=false;
        int tempBefore=0;
        int rule2=0;
        int rule2total=0;
        boolean invalidSubtractiveNumeral=false;
        int temp=0;
        boolean VLDcheck=false;
        boolean illegalThreeInARowState=false;
        int rangeLower=0;
        int rangeUpper=0;
        String checkComplete[] = new String[subtractiveNumerals.length];
        //-----------------------------------------
        // This has been completed outside main loop because it is processing a string to check values
        // this needs to go inside main loop. otherwise can not check the index of posValues
        
        System.out.println("In rule 4");
        
        for (int i=0; i<subtractiveNumerals.length; i++) // this is going through all 6 combos IV, IX, XL.....
        {
            System.out.println("***********************");
            System.out.println("Which lop number i:" + i);
            
            for (int j=0; j<subtractiveNumerals.length; j++ ) // this is going through all 6 combos IV, IX, XL.....
            {
                System.out.println("Which lop number j:" + j);
                
                // NEED MORE LOGIC TO PREVENT IT FROM COMPARING AGAINST ITSELF.
                // OTHERWISE IT WILL PREVENT SINGLE OCCURENCE OF SUBTRACTIVE NOTATION FROM BEING PROCESSED
                
                if (j==i)
                {
                    continue;
                }
                
                // this ensures that there are matches against two subtractive notations before processing
                if (numeralsToString.indexOf(subtractiveNumerals[i])!=-1 && numeralsToString.indexOf(subtractiveNumerals[j])!=-1)
                {
                    FlagSet=true;
                    twoSubtractiveNotations = true;
                    System.out.println("TWO SUBTRACTIVE NOTATIONS FOUND:");
                    System.out.println("***************************");
                    // this checks if subtractive notation lower value appears at index before higher subtractive notation

                    if (numeralsToString.indexOf(subtractiveNumerals[i]) < numeralsToString.indexOf(subtractiveNumerals[j]))
                    {
                        checkComplete[i]=subtractiveNumerals[i]+subtractiveNumerals[j];
                        
                        if(checkComplete[i].indexOf(subtractiveNumerals[j])==-1)
                        {
                            // THERE IS ISSUE IN THIS PART OF CODE:
                            // FOR INSTANCE IF IT DETECTS M CM IV It will first find circumstance ok since IV is in i loop and CM is in j loop
                            //and hence since index of IV will appear higher, it will decide not to proceed with this.
                            // HOWEVER as the i loop progresses it will become CM in i loop.. It will then find IV in the j loop.
                            // In this instance CM will appear lower in the index notation... hence the loop will validate as true and proceed.
                            // Need a way to stop this from occuring.
                            
                            System.out.println(numeralsToString + " is invalid");
                            System.out.println("Incorrect roman numeral. " + subtractiveNumerals[i] + " portion should be before: " + subtractiveNumerals[j]);
                            System.out.println("A group of numerals written in subtractive notation, of lower value, " + subtractiveNumerals[i] + " ( =" + subtractiveNumeralsRange[i][1]+"), cannot precede another group of numerals written in subtractive notation," + subtractiveNumerals[j] + " ( =" + subtractiveNumeralsRange[j][1]+").");
                            illegalSubtractive=true;

                            invalidSubtractiveNumeral=true;
                        }
                    }
                    // this now checks the subtractive notations in correct order
                    if (numeralsToString.indexOf(subtractiveNumerals[i]) > numeralsToString.indexOf(subtractiveNumerals[j]))
                    {
                        //Both these subtractive numerals appear. a case of now checking if range is same
                        System.out.println(subtractiveNumerals[i]);
                        System.out.println("This should print out start of the range:" + subtractiveNumeralsRange[i][0]);
                        System.out.println("This should print out end of the range:" + subtractiveNumeralsRange[i][1]);
                        System.out.println(subtractiveNumerals[j]);
                        System.out.println("This should print out start of the range:" + subtractiveNumeralsRange[j][0]);
                        System.out.println("This should print out end of the range:" + subtractiveNumeralsRange[j][1]);

                        if (subtractiveNumeralsRange[i][0] == subtractiveNumeralsRange[j][0]) // these subtractive notations are in the same range
                        {
                            System.out.println(subtractiveNumerals[i] + " is in the range: " + subtractiveNumeralsRange[i][0] + " - " + subtractiveNumeralsRange[i][1]);
                            System.out.println(subtractiveNumerals[j] + " is in the range: " + subtractiveNumeralsRange[j][0] + " - " + subtractiveNumeralsRange[j][1]);
                            System.out.println("They are both in the same range");
                            processedConversion[numeralsToString.indexOf(subtractiveNumerals[i])]=1;
                            temp = numeralsToString.indexOf(subtractiveNumerals[i]) + 1;
                            processedConversion[temp]=1;
                            System.out.println("REACH HERE!!!!!!!!!!");
                            processedConversion[numeralsToString.indexOf(subtractiveNumerals[j])]=1;
                            temp = numeralsToString.indexOf(subtractiveNumerals[j]) + 1;
                            processedConversion[temp]=1;
                            rule4=0;
                            
                        }
                        if (subtractiveNumeralsRange[i][0] != subtractiveNumeralsRange[j][0]) // this ensures that subtractive notations are not in the same range
                        {
                            if(processedConversion[numeralsToString.indexOf(subtractiveNumerals[i])]!=1 && processedConversion[numeralsToString.indexOf(subtractiveNumerals[j])]!=1 )
                            {
                                if (numeralsToString.indexOf(subtractiveNumerals[i])!=-1 && numeralsToString.indexOf(subtractiveNumerals[j])!=-1)
                                {
                                    System.out.println("correct order");
                                    correctOrder=true;
                                    System.out.println(subtractiveNumerals[i] + " " + numeralsToString.indexOf(subtractiveNumerals[i]));
                                    System.out.println(subtractiveNumerals[j] + " " + numeralsToString.indexOf(subtractiveNumerals[j]));
                                    //CAREFUL THESE BEEN COMMENTED
                                    processedConversion[numeralsToString.indexOf(subtractiveNumerals[i])]=1;
                                    temp = numeralsToString.indexOf(subtractiveNumerals[i]) + 1;
                                    processedConversion[temp]=1;
                                    processedConversion[numeralsToString.indexOf(subtractiveNumerals[j])]=1;
                                    temp = numeralsToString.indexOf(subtractiveNumerals[j]) + 1;
                                    processedConversion[temp]=1;
                                    
                                    switch (subtractiveNumerals[i])
                                    {
                                        case "IV":
                                        runningTotal = runningTotal + 4;
                                        break;
                                        
                                        case "IX":
                                        runningTotal = runningTotal + 9;
                                        break;

                                        case "XL":
                                        runningTotal = runningTotal + 40;
                                        break;
                                        
                                        case "XC":
                                        runningTotal = runningTotal + 90;
                                        break;
                                        
                                        case "CD":
                                        runningTotal = runningTotal + 400;
                                        break;
                                        
                                        case "CM":
                                        runningTotal = runningTotal + 900;
                                        break;
                                        
                                        default:
                                        invalidSubtractiveNumeral = true;
                                    }
                                    
                                    switch (subtractiveNumerals[j])
                                    {
                                        case "IV":
                                        runningTotal = runningTotal + 4;
                                        break;
                                        
                                        case "IX":
                                        runningTotal = runningTotal + 9;
                                        break;
                                        
                                        case "XL":
                                        runningTotal = runningTotal + 40;
                                        break;
                                        
                                        case "XC":
                                        runningTotal = runningTotal + 90;
                                        break;

                                        case "CD":
                                        runningTotal = runningTotal + 400;
                                        break;
                                        
                                        case "CM":
                                        runningTotal = runningTotal + 900;
                                        break;

                                        default:
                                        invalidSubtractiveNumeral = true;
                                    }
                                }
                            }
                        }
                    }
                }
            }
            
            // this confirms if a match is found. -1 value is no match. 0 is a match.
            System.out.println(subtractiveNumerals[i] + " " + numeralsToString.indexOf(subtractiveNumerals[i]));
            
            boolean correctOrder=false;
            System.out.println("total after rule4:" + rule4);
            // this now is just simply going through all subtractive notations if there is no other existing
            // this can not run if the above circumstance is true.
            //System.out.println("Was not expecting this loop to enter with " + subtractiveNumerals[i] + subtractiveNumerals[j]);
            System.out.println(twoSubtractiveNotations);
            
            if (!twoSubtractiveNotations)
            {
                System.out.println("What is I:" + i);
                System.out.println("BE HERE!!!!!!!!!!!!!!!!!!!!!!!!!!!");

                if (numeralsToString.indexOf(subtractiveNumerals[i])!=-1) // This double checks that there is only one subtractive notation
                {
                    System.out.println("BE HERE AGAIN!!!!!!!!!!!!!!!!!!!!!!!!!!!");
                    //if (processedConversion[numeralsToString.indexOf(subtractiveNumerals[i])]!=1)
                    //{
                    System.out.println("BE HERE AGAIN2!!!!!!!!!!!!!!!!!!!!!!!!!!!");
                    // **This is now checking if X for instance is occuring in the numerals and also subtractive notations
                    // ** for instance XCX
                    //the code has not referenced range at all.. this will cause code to fail in scenarios such as MCM where it is VALID
                    
                    System.out.println("ASDASDBGDFSDGFDGFDG");
                    System.out.println(subtractiveNumerals[i]);
                    runningTotal = runningTotal + subtractiveNumeralsRange[i][1];
                    
                    if (numeralsToString.indexOf(subtractiveNumerals[i])!=-1)
                    // if it finds a match of subtractive notation in the numeral consisting of 3 or more numerals
                    {
                        System.out.println(numeralsToString.indexOf(subtractiveNumerals[i]));
                        // this ensures if numeral appears after notation, it gets position 2
                        if (numeralsToString.indexOf(subtractiveNumerals[i])>=0 && numeralsToString.indexOf(subtractiveNumerals[i]) + 2<=posValues.length-1)
                        {
                            tempA = numeralsToString.indexOf(subtractiveNumerals[i])+2;
                            System.out.println("NUMERAL AFTER NOTATION!");
                        }
                        // at this point we know that subtractive notations are legitimate, hence can perform extra step
                        // this ensures if numeral appears before notation, it gets position one place before
                        // it should only also go here lets say for example value before notation is bigger than range of the subtractive notation
                        // for instance MIV it should not go there. Reason is this would ensure for such a numeral as MIVC it compares forward as oppose backware
                        // unsure if this logic will hold.. perhaps better to do
                        //if (numeralsToString.indexOf(subtractiveNumerals[i])!=0
                        
                        if (numeralsToString.indexOf(subtractiveNumerals[i])!=0 /*&& posValues[temp][1]>subtractiveNumeralsRange[i][1] */ )
                        {
                            tempB = numeralsToString.indexOf(subtractiveNumerals[i])-1;
                            valueBeforeSubtractiveNotation = true;
                            tempBefore= numeralsToString.indexOf(subtractiveNumerals[i]);
                            System.out.println("NUMERAL BEFORE NOTATION!");
                        }
                        
                        //temp = numeralsToString.indexOf(subtractiveNumerals[i]) + 2; // sets temp to allow comparison 1st with 3rd char
                        System.out.println("vcbvbnm,,");
                        System.out.println(posValues.length-1);
                        System.out.println(numeralsToString.indexOf(subtractiveNumerals[i]));
                        // NEED MORE LOGIC HERE TO CHANGE HOW TEMP IS GENERATED
                        // FOR INSTANCE WITH XCM temp is one places before than location of index notation
                        //HOWEVER WITH MCM the M is one place before subtractive notation
                        //So need to check in both directions
                        System.out.println("first");
                    }
                    
                    // this is length of two inputtedNumerals. It has no bearing on above.
                    if (numeralsToString.indexOf(subtractiveNumerals[i])!=-1 && posValues.length==2) //this should allow normal flow of app?
                    {
                        temp = numeralsToString.indexOf(subtractiveNumerals[i]) + 1;
                        System.out.println("second");
                    }
                    
                    System.out.println("temp is currrentl: " + temp);
                    System.out.println("WWWWWWWWWWWWWWWWWWWWWWWWWWWW");
                    System.out.println("What is I:" + i);
                    
                    if (temp<=posValues.length && posValues.length>2 )
                    {
                        // this ensures that there is a value in numeral to compare against
                        // it is set to minumum 3 numerals
                        //This checks XCX first char of subtractivenotation X against 2 positions in main array
                        //System.out.println("B:" + numeralsToString.charAt(temp-1));
                        //now need to know the range of the subtractive notation and also the non notation
                        // which is either before or after subtractive notation
                        // VERY IMPORTANT
                        //since the code does not include array holding the numeral and its decimal value, switch statement
                        // will need to be used. posValues was declared two dimensional holding.
                        //Also since something like XC, the index will be split in two and lower and upper range will be outputted.
                        //range for subtractive notation
                        
                        switch (subtractiveNumerals[i].charAt(0))
                        {
                            case 'I':
                            rangeLower=1;
                            break;

                            case 'V':
                            rangeLower=5;
                            break;
                            
                            case 'X':
                            rangeLower=10;
                            break;

                            case 'L':
                            rangeLower=50;
                            break;

                            case 'C':
                            rangeLower=100;
                            break;
                            
                            case 'D':
                            rangeLower=500;
                            break;

                            case 'M':
                            rangeLower=1000;
                            break;
                            
                            default:
                            System.out.println("Do not reach here");
                        }
                        
                        switch (subtractiveNumerals[i].charAt(1))
                        {
                            case 'I':
                            rangeUpper=1;
                            break;

                            case 'V':
                            rangeUpper=5;
                            break;
                            
                            case 'X':
                            rangeUpper=10;
                            break;

                            case 'L':
                            rangeUpper=50;
                            break;
                            
                            case 'C':
                            rangeUpper=100;
                            break;

                            case 'D':
                            rangeUpper=500;
                            break;
                            
                            case 'M':
                            rangeUpper=1000;
                            break;

                            default:
                            System.out.println("Do not reach here");
                        }
                        
                        // This is now the example for XC X X=10 range for XC (is 10-90 )
                        // So evaluating that value at location is not greater or equal to 10
                        //if (tempBefore>0) // this is showing there is check backwards
                        //examples would be CCM
                        
                        if (/*subtractiveNumerals[i].charAt(0) == numeralsToString.charAt(tempBefore) &&*/ posValues[tempB][1] <(subtractiveNumeralsRange[i][1]) && tempBefore>tempB)
                        {
                            System.out.println("2. A numeral (a letter) of lower value" + numeralsToString.charAt(tempB) + "(=" + posValues[tempB][1] + ") "+ "cannot precede a group of numerals written in subtractive notation,");
                            System.out.println(subtractiveNumerals[i] + "( ="+ subtractiveNumeralsRange[i][1] +").");
                            //C CM: A numeral (a letter) of lower value, C ( = 100), cannot precede a group of
                            //numerals written in subtractive notation, CM ( = 900).
                            illegalSubtractive=true;
                        }
                        
                        //temp is set +2 from index of start subtractive notation
                        if (posValues[tempA][1] >=subtractiveNumeralsRange[i][0] && posValues[tempA][1] <=subtractiveNumeralsRange[i][1] && tempA>tempBefore) /*&& posValues.length>2*/
                        {
                            System.out.println("%*%*%*");
                            System.out.println("1. The numeral " + numeralsToString.charAt(tempA) + "(=" + posValues[tempA][1] + ") " + " cannot be placed after a group of numerals written in subtractive notation: " + subtractiveNumerals[i]);
                            System.out.println("Of the same range: " + "( = " + subtractiveNumeralsRange[i][0] + "-" + subtractiveNumeralsRange[i][1] + ").");
                            //The numeral X ( = 10) cannot be placed after a group of numerals written in subtractive notation, XC ( = 90),
                            //of the same range value (10 - 90)
                            illegalSubtractive=true;
                        }
                        
                        // this is now using scenario such as C CM where C (100) appears before CM(subtractive numeral) -range (100-900)
                        // C can not be lower than 900(upper range). It can be equal for scenarios such as MCM (this is valid 1900).
                        // This is using IV C as an EXAMPLE
                        //1 has been subtracted from posValues since it is zero index based
                        //This in the if loop will ensure instances such as M CM are not trapped
                        //However C CM is trapped
                        // RangeUpper!= posValues[temp-1][1]
                        //using real example IVC that ends up in here
                        //this rule has to work in tempB and tempA
                        //example is MIVC since it will pass on MIV section but fail on IVC section
                        // this is looking at perspective of M IV C (examining IV in relation to C)
                        
                        if (subtractiveNumeralsRange[i][1] < posValues[tempA][1] && tempBefore<tempA) /*&& posValues.length>2*/
                        {
                            System.out.println("%*%*%*");
                            System.out.println("3ver1. A group of numerals written in subtractive notation, of lower value,");
                            System.out.println(subtractiveNumerals[i] + " ( = " + (rangeUpper-rangeLower) + "), cannot precede a numeral of larger value, " + numeralsToString.charAt(tempA) + "( = "+posValues[tempA][1]+").");
                            //IV C: A group of numerals written in subtractive notation, of lower value, IV ( = 4),
                            //cannot precede a numeral of larger value, C ( = 100)
                            //System.out.println("1. The numeral " + numeralsToString.charAt(temp) + "(=" + posValues[temp][1] + ") " + " cannot be placed after a group of numerals written in subtractive notation: " + subtractiveNumerals[i]);
                            //System.out.println("Of the same range: " + "( = " + rangeLower + "-" + rangeUpper + ").");
                            
                            illegalSubtractive=true;
                        }
                        
                        // this is looking at perspective of M IV C (examining IV in relation to M)
                        if (subtractiveNumeralsRange[i][1] > posValues[tempB][1] && tempBefore>tempB) /*&& posValues.length>2*/
                        {
                            System.out.println("%*%*%*");
                            System.out.println("3ver2. A group of numerals written in subtractive notation, of higher value,");
                            System.out.println(subtractiveNumerals[i] + " ( = " + (rangeUpper-rangeLower) + "), cannot proceed a numeral of lower value, " + numeralsToString.charAt(tempB) + "( = "+posValues[tempB][1]+".");
                            //IV C: A group of numerals written in subtractive notation, of lower value, IV ( = 4),
                            //cannot precede a numeral of larger value, C ( = 100)
                            
                            illegalSubtractive=true;
                        }
                        
                        // THIS CODE IS REQUIRED FOR EXAMPLE SUCH AS IVC
                        //CAREFUL
                        // this is now checking if such a sequence exists CMM. This is not legal since
                        //subtractive notation CM (900) is less than M (1000).
                        
                        switch (subtractiveNumerals[i])
                        {
                            case "IV":
                                rule4Single = rule4Single + 4;
                                break;
                            
                            case "IX":
                                rule4Single = rule4Single + 9;
                                break;
                            
                            case "XL":
                                rule4Single = rule4Single + 40;
                                break;
                            
                            case "XC":
                                rule4Single = rule4Single + 90;
                                break;
                            
                            case "CD":
                                rule4Single = rule4Single + 400;
                                break;
                            case "CM":
                                rule4Single = rule4Single + 900;
                                break;
                            
                            default:
                                invalidSubtractiveNumeral = true;   
                        }
                        
                        twoSubtractiveNotations=false;
                        singleSubtractiveNotations=true;
                    }
                    
                    processedConversion[numeralsToString.indexOf(subtractiveNumerals[i])]=1;
                    temp = numeralsToString.indexOf(subtractiveNumerals[i]) + 1;
                    processedConversion[temp]=1;
                }
            }
        }
        
        // MAIN PROGRAM EXECUTION
        //this will examine decimal number stored. If identical numerals in consecutive it will add to the total.
        for (int m=1; m<posValues.length; m++) // this is starting not at zero index since compared to previous value
        {
            if (processedConversion[m]!=1)
            {
                //posValues[m][0]=numeral position //[m][1]=decimal
                // This section is best completed examining string of the character array of inputted numerals.
                // Rule 3: The letters V, L, and D are not repeated.
                // There are acceptedNumerals[1], acceptedNumerals[3], acceptedNumerals[5]
                // posValues[m][0] stores information relevant
                //{'M','D','C','L','X', 'V','I'};
                
                System.out.println("Going into rule 3");
                if (!VLDcheck)
                {
                    for (indexCount=0; indexCount<posValues.length; indexCount++)
                    {
                        System.out.println("value of indexCount: " + indexCount);
                        System.out.println(posValues.length);
                        
                        if (posValues[indexCount][1]==5)
                        {
                            countV++;
                            System.out.println("found a V");
                        }
                        
                        if (posValues[indexCount][1]==50)
                        {
                            countL++;
                        }
                        
                        if (posValues[indexCount][1]==500)
                        {
                            countD++;
                        }
                    }
                }
                
                VLDcheck=true;
                
                //Rule 1: When certain numerals are repeated, the number represented by them is their sum. For example, II = 1 + 1 = 2, or XX = 10 + 10 = 20, or, XXX = 10 + 10 + 10 = 30.
                
                if (posValues[m][1]==posValues[m-1][1]) // this is comparing decimal number for numeral against previous one
                {
                    // Rule 2: It is to be noted that no Roman numerals can come together more than 3 times. For example, we cannot write 40 as XXXX
                    // This needs to work from ZeroIndex not m
                    System.out.println("starting rule 1");
                    //if (m!=(posValues.length-2) && posValues.length>3) // what does this rule mean, first part
                    
                    if (posValues.length>3)
                    // m is current position in the numerals array
                    {
                        // has to be 3 advancing numerals to check if 4 together
                        if (m<=posValues.length-3) // can not check for three in row if last element in array
                        {
                            //if (temp1+2<=posValues.length)
                            //{  // checking for three in row same
                            if (temp1+3<=posValues.length)
                            {
                                for (int counter=0;counter<=posValues.length-3;counter=counter+4)
                                {
                                    System.out.println("Value of coutner: " + counter);
    if (posValues[temp1][1]==posValues[temp1+1][1] && posValues[temp1][1]==posValues[temp1+2][1] && posValues[temp1][1]==posValues[temp1+3][1])
                                    {
                                        System.out.println("Four in a row occurrence of: ");
                                        illegalFourInARowState=true;
                                    
                                        System.out.println("********************************************************");
                                        System.out.println("This is temp1 99:" + temp1);
                                        System.out.println("********************************************************");

                                        threeInRow = (posValues[temp1][1] * 3) +threeInRow;
                                        temp1 = temp1+4;

                                        System.out.println("********************************************************");
                                        System.out.println("This is new temp1 :" + temp1);
                                        System.out.println("********************************************************");

                                        if (temp1+3>posValues.length)
                                        {
                                            break;
                                        }
                                    }
                                }
                            }
                        }
                    }
                    
                    if (!illegalFourInARowState)
                    {
                        System.out.println("Amit Amlani");
                        
                        if (processedConversion[m]!=1 && processedConversion[m-1]!=1)
                        {
                            rule2total=posValues[m][1]+posValues[m-1][1];
                            rule2=rule2+rule2total; // they will be totalled if same
                            System.out.println("So far sum:" + rule2);
                            rule2State=true;
                        }
                        
                        valueConsecutiveOccurences[m] = posValues[m][1]; //storing decimal value in array.
                        consecutiveOccurrences=consecutiveOccurrences+2;
                        // valueConsecutiveOccurences[m] this keeps a track of the roman numeral that has been repeating
                        //num++;
                        // this checks if there has already been consecutive occurence of the numeral adjacently
                        //[m][0]=numeral position //[m][1]=decimal
                        if (m!=(posValues.length-1))
                        {
                            if (valueConsecutiveOccurences[m]==posValues[m+1][1] && processedConversion[m+1]!=1)
                            {
                                System.out.println("does this happen45");
                                rule2=rule2-(rule2total/2);
                                rule2total=0;
                            }
                        }
                        
                        // NEED TO VERIFY THIS
                        if (illegalThreeInARowState)
                        {
                            rule2=0;
                        }
                    }
                }
                
                //Rule 5: When a Roman numeral is placed after another Roman numeral of greater value,
                //the result is the sum of the numerals. For example, VIII = 5 + 1 + 1 + 1 = 8, or,
                //XV = 10 + 5 = 15,
                // This appears to be where the code has determined if numerals are in some decent order
                System.out.println("What is value of zeroindexcount: " + zeroIndexCount);
                
                if (posValues[m][1]<posValues[m-1][1])
                {
                    System.out.println("How many times does it enter in this section");
                    System.out.println("What is m: " + posValues[m][1]);
                    System.out.println("What is m-1: " + posValues[m-1][1]);
                    //System.out.println("This is value marked with 1: " + posValues[processedConversion[numeralsToString.indexOf(subtractiveNumerals[m])][1]]);
                    //********************Need to be careful here of making it already set to 1

//System.out.println("This is value marked with 1: " + posValues[processedConversion[numeralsToString.indexOf(subtractiveNumerals[m])-1][1]]);
                    if (processedConversion[m-1]!=1)
                    {
                        rule5total = posValues[m][1] + posValues[m-1][1];
                        rule5 = rule5total + rule5;
                        System.out.println("*******RULE5******: " + rule5);
                        rule5total = 0;
                        rule5State=true;
                        //processedConversion[m]=1;
                        //UNSURE
                        //processedConversion[m-1]=1;
                        if (posValues.length==2)
                        {
                            //processedConversion[m-1]=1;
                        }
                        
                        if (m!=1) // if not the first numeral
                        {
                            if (rule4Single!=0)
                            {
                                System.out.println("!!!!!!!!!!!!!!!!!!!!!!!");
                                //rule5=rule4Single + posValues[m][1];
                                rule5=posValues[m][1] + posValues[m-1][1];
                            }
                        }
                    }
                }
                
                System.out.println("at rule 6: " + total1);
                //Rule 6: When a Roman numeral is placed before another Roman numeral of greater value,
                //the result is the difference between the numerals. For example, IV = 5 - 1 = 4, or, XL = 50 - 10 = 40,
                //or XC = 100 - 10 = 90
                
                System.out.println("Rule 6");
                System.out.println("Must WORK!!!!");
                System.out.println(zeroIndexCount);
                System.out.println(posValues[zeroIndexCount][1]);
                
                if (posValues[zeroIndexCount][1]<posValues[zeroIndexCount+1][1])
                {
                    if (posValues[zeroIndexCount][1]==1 && posValues[zeroIndexCount+1][1]>10)
                    {
                        System.out.println("Roman Numeral I can not precede: " + posValues[zeroIndexCount+1][1]);
                        IplacedIncorrect=true;
                    }
                    
                    if (posValues[zeroIndexCount][1]==10 && posValues[zeroIndexCount+1][1]>100)
                    {
                        System.out.println("Roman Numeral X can not precede: " + posValues[zeroIndexCount+1][1]);
                        IplacedIncorrect=true;
                    }
                    
                    if (posValues[zeroIndexCount][1]==50 && posValues[zeroIndexCount+1][1]>=50)
                    {
                        System.out.println("Roman Numeral L can not precede: " + posValues[zeroIndexCount+1][1]);
                        IplacedIncorrect=true;
                    }
                    
                    if (posValues[zeroIndexCount][1]==5 && posValues[zeroIndexCount+1][1]>posValues[zeroIndexCount][1])
                    {
                        System.out.println("Roman Numeral V can not precede: " + posValues[zeroIndexCount+1][1]);
                        IplacedIncorrect=true;
                    }
                    
                    if (posValues[zeroIndexCount][1]!=5 && posValues[zeroIndexCount][1]!=50 && posValues[zeroIndexCount][1]!=500 && !IplacedIncorrect)
                    {
                        processedConversion[zeroIndexCount]=1;
                        rule6total = posValues[zeroIndexCount+1][1] - posValues[zeroIndexCount][1];
                        rule6 = rule6total + rule6;
                        rule6total = 0;
                        rule6State=true;
                    }
                    else
                    { 
                        System.out.println("Illegal subtractive notation found with V, D or L");
                        rule5=0;
                        illegalSubtractive=true;
                    }
                }
                
                // Rule 7: When a Roman numeral of a smaller value is placed between two numerals of greater value,
                //it is subtracted from the numeral on its right. For example, XIV = 10 + (5 - 1) = 14,
                //or, XIX = 10 + (10 - 1) = 19
                System.out.println("Rule 7");
                // rule 7 will not stall by rule 4 since the the right hand side character in rule 4 is always bigger.
                if (m!=posValues.length && posValues.length>2) // a numeral can not be in middle if it is the last in the numeral array
                // it also can not be in middle if the first numeral. Hence using m index notation.
                {
                    if (processedConversion[m]!=1)
                    {
                        //START FROM HERE AND TEST XI
                        if (m!=posValues.length-1)
                        {
                            if (posValues[m][1]<posValues[m-1][1] && posValues[m][1]<posValues[m+1][1])
                            {
                                //System.out.println("what " + (m-1));
                                //processedConversion[m]=1;
                                //System.out.println("This is value marked with 1: " + posValues[processedConversion[numeralsToString.indexOf(subtractiveNumerals[m])][1]]);
                                //processedConversion[m+1]=1;
//System.out.println("This is value marked with 1: " + posValues[processedConversion[numeralsToString.indexOf(subtractiveNumerals[m+1])][1]]);
                                rule7total = posValues[m+1][1] - posValues[m][1];
                                rule7 = rule7total + rule7;
                                rule7total = 0;
                                System.out.println("total at rule 7:" + rule7);
                            }
                        }
                    }
                }
                
                zeroIndexCount++;
                temp1++;
                System.out.println("This is overall total:" + (total1));
            }
        }
        
        // THIS WILL NOW CHECK IF EACH NUMBER HAS OR HAS NOT BEEN PROCESSED IN CHECKING SO far
        int counter=0;
        int unTotal=0;
        
        for (int c: processedConversion)
        {
            System.out.println("This is value of c: " + c);
            System.out.println("This is the numeral value: " + posValues[counter][1]);
            
            if (c!=1)
            {
                unTotal = posValues[counter][1] + unTotal;
                System.out.println("This has not been added to the total" + unTotal);
                System.out.println("This is the position: " + counter);
            }
            
            counter++;
        }
        
        // this is part of rule 3
        if (countD>1 || countL>1 || countV>1)
        {
            System.out.println("Invalid roman numeral. Numeral V or D or L has occured more than once");
            rule3Fail = true;
        }

        if (inputtedNumerals.length==2) // checking number with 2 numerals
        {
            if (posValues[0][0]==posValues[1][0] && rule3Fail==false) // if values identical straight forward conversion
            {
                twoNumerals = posValues[0][1] + posValues[1][1];
                System.out.println("Conversion is double:" + (twoNumerals));
                //System.out.println("XL: " + posValues[0][1]);
                processedConversion[0]=1;
                processedConversion[1]=1;
                //System.out.println("This is value marked with 1: " + posValues[1][1]);
            }
        }
        
        // THIS WILL NOW CHECK IF EACH NUMBER HAS OR HAS NOT BEEN PROCESSED IN CHECKING SO far
        // it is not picking up MM or II
        // This suggests that they have been marked as processedconversion
        if (!illegalSubtractive && !IplacedIncorrect && !rule3Fail && !illegalFourInARowState)
        {
            if (runningTotal>0 && unTotal==0 && FlagSet==true)
            {
                runningTotal = runningTotal / 2;
            }
            
            validNumber=true;
            System.out.println("\n\n********************* GRAND TOTAL*************");
            System.out.println("NOTE: Code is designed for up to MMMM=4000 due to notation changes henceforth");
            System.out.println(numeralsToString + " is a VALID roman numeral");
            System.out.println("runningTotal:" + runningTotal);
            System.out.println("Not added total:" + unTotal );
            System.out.println("**TOTAL: " + (runningTotal+unTotal));
            System.out.println("**********************************");
            //System.exit(0);
        }
        
        if (!validNumber)
        {
            System.out.println("\n\n********************* GRAND TOTAL*************");
            System.out.println(numeralsToString + " is an INVALID roman numeral");
            System.out.println("Address the issues outputted for a valid Roman numeral");
            System.out.println("**********************************");
        }
        
        System.out.println("\n\n\n********************************************");
        System.out.println("OLD PROGRAMME LOGIC");
        System.out.println("\n********************************************");
        System.out.println(numeralsToString + " is the roman numeral");
        System.out.println("number of Vs: " + countV);
        System.out.println("number of Ls: " + countL);
        System.out.println("number of Ds: " + countD);
        System.out.println("rule4: " + rule4);
        System.out.println("rule2: " + rule2);
        System.out.println("rule4Single: " + rule4Single);
        System.out.println("rule5: " + rule5);
        System.out.println("rule6: " + rule6);
        System.out.println("rule7: " + rule7);
        System.out.println("threeinarow:" + threeInRow);
        System.out.println("Untotal:" + unTotal);
        
        if (rule3Fail)
        {
            System.out.println("More than 2 instances of V, L and D:");
            System.out.println("D: " + countD);
            System.out.println("V: " + countV);
            System.out.println("L: " + countL);
            //System.exit(0);
        }
        
        if (!illegalSubtractive && !IplacedIncorrect && !illegalThreeInARowState && !rule3Fail)
        {
            if (unTotal!=0 && rule6!=0 && rule5!=0 && rule4Single!=0 && rule2!=0)
            {
                System.out.println("total1_temp: " + (rule4Single + unTotal));
                System.exit(0);
            }

            if (unTotal!=0 && rule6!=0 && rule5!=0 && rule4Single!=0)
            {
                System.out.println("total1: " + (rule4Single + unTotal + rule5));
                System.exit(0);
            }
            
            if (unTotal!=0 && rule6==0 && rule5==0 && threeInRow!=0)
            {
                System.out.println("total2_temp: " + (rule4Single + unTotal + threeInRow));
                System.exit(0);
            }
            
            if (rule4Single!=0 && unTotal!=0)
            {
                System.out.println("total2: " + (rule4Single + unTotal));
                System.exit(0);
            }
            
            if (rule4Single!=0 && unTotal!=0 && rule2!=0 )
            {
                System.out.println("total4_temp: " + (rule4Single + unTotal));
                System.exit(0);
            }
            
            if (rule4Single==0 && rule2!=0 && rule5!=0 && rule4!=0)
            {
                System.out.println("total4: " + (rule4 + rule2 + rule5));
                System.exit(0);
            }
            
            if (rule4Single==0 && rule2!=0 && rule5!=0 && rule4!=0)
            {
                System.out.println("total4: " + (rule4 + rule2 + rule5));
                System.exit(0);
            }
            
            if (unTotal==0 && rule5==0 && rule2==0 && rule4==0 && threeInRow!=0)
            {
                System.out.println("Total5: " + (threeInRow));
                System.exit(0);
            }
            
            if (unTotal!=0 && rule5!=0 && rule6!=0)
            {
                System.out.println("Total6: " + (unTotal+rule6));
                System.exit(0);
            }
            
            if (unTotal!=0 && rule5!=0 &&rule2!=0)
            {
                System.out.println("Total6: " + (unTotal));
                System.exit(0);
            }
            
            if (unTotal!=0 && rule5==0 && rule2==0 && rule4==0 && threeInRow!=0)
            {
                System.out.println("Total7: " + (unTotal+threeInRow));
                System.exit(0);
            }
            
            if (rule2!=0 && rule4Single==0 && rule5==0 && rule6==0 && threeInRow!=0)
            {
                System.out.println("Total8: " + (threeInRow+rule2));
                System.exit(0);
            }
            
            if (rule2!=0 && rule4Single==0 && rule5==0 && rule6==0 && unTotal!=0)
            {
                System.out.println("Total9: " + (rule2));
                System.exit(0);
            }
            
            if (rule2!=0 && rule4Single==0 && rule5==0 && rule6==0)
            {
                System.out.println("Total10: " + rule2);
                System.exit(0);
            }
            
            if (rule4Single!=0 && rule5!=0 && rule6!=0)
            {
                System.out.println("Total11: " + (rule4Single+rule5));
                System.exit(0);
            }
            
            if (unTotal!=0 && rule5==0 && rule2==0 && rule4==0 && rule4Single==0)
            {
                System.out.println("Total12: " + (unTotal));
                System.exit(0);
            }
            
            if (unTotal!=0 && rule4!=0)
            {
                System.out.println("Total13: " + (unTotal + rule4));
                System.exit(0);
            }
            
            
            if (rule5!=0 && rule6!=0 && unTotal!=0)
            {
                System.out.println(numeralsToString + "is an invalid roman numeral");
                System.out.println(numeralsToString + "INVESTIGATE CODE OR CONDITIONAL IF LOOPS FOR TOTAL IF ENTER OCCURS");
                System.exit(0);
            }
            
            if (rule6!=0 && rule5!=0)
            {
                System.out.println("Total14: " + (rule6+rule5));
                System.exit(0);
            }
            
            if (rule6!=0 && rule2!=0)
            {
                System.out.println("Total 15: " + (rule6+rule2));
                System.exit(0);
            }
            
            
            if (rule5!=0 && rule2!=0 && threeInRow==0 && rule4Single!=0)
            {
                System.out.println("Total16: " + (rule5+rule2));
                System.exit(0);
            }
            
            if (rule5!=0 && rule2!=0 && threeInRow!=0)
            {
                System.out.println("Total17: " + (rule5+rule2));
                System.exit(0);
            }
            
            if (rule5!=0 && rule2!=0)
            {
                System.out.println("Total18: " + (rule5+rule2));
                System.exit(0);
            }
            
            if (rule5!=0 && unTotal!=0)
            {
                System.out.println("Total19: " + (rule5+unTotal));
                System.exit(0);
            }
            
            if (rule5!=0 && rule4!=0)
            {
                System.out.println("Total20: " + (rule5 + rule4));
                System.exit(0);
            }
            
            if (rule5!=0 && threeInRow!=0 && rule4Single!=0)
            {
                System.out.println("Total21: " + (rule5+threeInRow));
                System.exit(0);
            }
            
            if (rule5!=0 && threeInRow!=0)
            {
                System.out.println("Total22: " + (rule5+threeInRow));
                System.exit(0);
            }
            
            if (rule5!=0)
            {
                System.out.println("Total23: " + (rule5));
                System.exit(0);
            }
            
            if (rule2!=0 && unTotal!=0 && rule4Single!=0)
            {
                System.out.println("Total24: " + (rule2 + unTotal + rule4Single));
                System.exit(0);
            }
            
            if (rule2!=0 && rule4Single!=0)
            {
                System.out.println("Total25: " + (rule2 + rule4Single));
                System.exit(0);
            }
            
            if (rule2!=0)
            {
                System.out.println("Total26: " + (twoNumerals));
                System.exit(0);
            }

            if (rule4Single!=0)
            {
                System.out.println("Total27 is: " + (unTotal + rule4Single));
                System.exit(0);
            }
            
            if (rule4!=0)
            {
                System.out.println("Total28 is: " + (rule4));
                System.exit(0);
            }
        }
        
        System.out.println(numeralsToString + " is NOT a VALID roman numeral");
        System.out.println("Address the issues outputted for a valid Roman numeral");
        //System.out.println("this is the overall sum: " + (rule2+rule4Single+rule5+rule6+rule7));
        // System.out.println("this is the overall sum: " + (rule5 + rule2));
        // This is the best logic found on the internet for roman numeral conversion.
        // Logic will be coded one by one and see if it works overall
        /*
It is necessary for us to remember the rules for reading and writing Roman numbers in order to avoid mistakes. Here is a list of the basic rules for Roman numerals.
Rule 1: When certain numerals are repeated, the number represented by them is their sum. For example, II = 1 + 1 = 2, or XX = 10 + 10 = 20, or, XXX = 10 + 10 + 10 = 30.
Rule 2: It is to be noted that no Roman numerals can come together more than 3 times. For example, we cannot write 40 as XXXX
Rule 3: The xcletters V, L, and D are not repeated.
Rule 4: Only I, X, and C can be used as subtractive numerals. There can be 6 combinations when we subtract. These are IV = 5 - 1 = 4; IX = 10 - 1 = 9; XL = 50 - 10 = 40; XC = 100 - 10 = 90; CD = 500 - 100 = 400; and CM = 1000 - 100 = 900
Rule 5: When a Roman numeral is placed after another Roman numeral of greater value, the result is the sum of the numerals. For example, VIII = 5 + 1 + 1 + 1 = 8, or, XV = 10 + 5 = 15,
Rule 6: When a Roman numeral is placed before another Roman numeral of greater value, the result is the difference between the numerals. For example, IV = 5 - 1 = 4, or, XL = 50 - 10 = 40, or XC = 100 - 10 = 90
Rule 7: When a Roman numeral of a smaller value is placed between two numerals of greater value, it is subtracted from the numeral on its right. For example, XIV = 10 + (5 - 1) = 14, or, XIX = 10 + (10 - 1) = 19
Rule 8: To multiply a number by a factor of 1000 a bar is placed over it.
Rule 9: Roman numerals do not follow any place value system.
Rule 10: There is no Roman numeral for zero (0).
*/
    }
}