public class Solution {
    public int RomanToInt(string s) {
           int num = 0;

                for (int i = s.Length - 1; i >= 0; i--)
                {


                    switch (s[i])
                    {

                        case 'I':
                            if (i + 1 != s.Length && s[i + 1] != s[i])
                                num--;
                            else
                                num++;
                            continue;
                        case 'V':
                            if (i + 1 != s.Length && s[i + 1] == 'X')
                                num -= 5;
                            else
                                num += 5;
                            continue;
                        case 'X':
                            if (i + 1 != s.Length && (s[i + 1] == 'L' || s[i + 1] == 'C'))
                                num -= 10;
                            else
                                num += 10;
                            continue;
                        case 'L':
                            num += 50;
                            continue;
                        case 'C':
                            if (i + 1 != s.Length && (s[i + 1] == 'D' || s[i + 1] == 'M'))
                                num -= 100;
                            else
                                num += 100;
                            continue;
                        case 'D':
                            num += 500;
                            continue;
                        default:
                            num += 1000;
                            continue;

                    }



                }
                return num;
    }
}