using System;

using System.Collections;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var testNumber = "IV";

        var test = GetOrdinalNumber(testNumber);

        Console.WriteLine(test);

    }

    public static int GetOrdinalNumber(string input)

    {

        var ordinalNumber = 0;

        Dictionary<string, string> romanNumbers = new Dictionary<string, string>();

        romanNumbers.Add("I","1");

        romanNumbers.Add("V","5");

        romanNumbers.Add("X","10");

        romanNumbers.Add("L","50");

        romanNumbers.Add("C","100");

        romanNumbers.Add("D","500");

        romanNumbers.Add("M","1000");

        Dictionary<string, string> complexRomanNumbers = new Dictionary<string, string>();

        complexRomanNumbers.Add("IV","4");

        complexRomanNumbers.Add("IX","9");

        complexRomanNumbers.Add("XL","40");

        complexRomanNumbers.Add("XC","90");

        complexRomanNumbers.Add("CD","400");

        complexRomanNumbers.Add("CM","900");

        foreach(var current in complexRomanNumbers)

        {

            input = input.Replace(current.Key, string.Format("-{0}", current.Value));

        }

​

        foreach(var current in romanNumbers)

        {

            input = input.Replace(current.Key, string.Format("-{0}", current.Value));

        }

        var finalArray = input.Split('-');

        foreach(var current in finalArray)

        {

            if (!string.IsNullOrEmpty(current)) 

            {

                ordinalNumber += Convert.ToInt32(current);

            }

        }

        return ordinalNumber;

    }

}