using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        Console.WriteLine($"III is 1 : {RomanToInt("I")}");

        Console.WriteLine($"III is 3 : {RomanToInt("III")}");

        Console.WriteLine($"XV is 15 : {RomanToInt("XV")}");

        Console.WriteLine($"IV is 4 : {RomanToInt("IV")}");

        Console.WriteLine($"IV is 8 : {RomanToInt("VIII")}");

        Console.WriteLine($"XV is 14 : {RomanToInt("XIV")}");

        Console.WriteLine($"MCMXCIV is 1994 : {RomanToInt("MCMXCIV")}");

    }

    public static int CalScale(char next, char c1, char c2)

    {

        return (next == c1 || next == c2) ? -1 : 1;

    }

     public static int RomanToInt(string s) {

        int total = 0, size = s.Length;

        for(int i = 0; i < size; i++)

        {

            char nextChar = (i + 1 < size ? s[i + 1] : '\0');

            switch(s[i])

            {

                case 'I': total += 1 * CalScale(nextChar, 'V', 'X'); break;

                case 'V': total += 5; break;

                case 'X': total += 10 * CalScale(nextChar, 'C', 'L'); break;

                case 'L': total += 50; break;

                case 'C': total += 100 * CalScale(nextChar, 'M', 'D'); break;

                case 'D': total += 500; break;

                case 'M': total += 1000; break;

                default:

                    Console.WriteLine("No Roman");

                    break;

            }

        } 

       return total;

    }

}