using System;

using System.Text;

public class Program

{

​

​

​

public static void Main(string[] args)

{

    string n1 = Console.ReadLine();

    decimal n = Convert.ToDecimal(n1);

​

    string k1 = Console.ReadLine();

    decimal k = Convert.ToDecimal(k1);

​

    string tempJ = Console.ReadLine();

    decimal j=0;

    if (tempJ == "I")

    {

        j = 6;

    }

    if (tempJ == "II")

    {

        j = 5;

    }

    if (tempJ == "III")

    {

        j = 4;

    }

​

    decimal a= jCk(j, k);

    decimal b = jCk((k-j), (n-j));

    decimal c = jCk(k, n);

    decimal r = a*b/c;

    Console.WriteLine(a.ToString("F10"));

}

static decimal jCk_helper(decimal j, decimal k)

{

    Console.WriteLine("in jckhelper k=" + k + " j=" + j);

    if (k == 0) return 1;

    return jCk_helper(j - 1, k - 1) * j / k;

}

​

static decimal jCk(decimal j, decimal k)

{

    Console.WriteLine("in jck k=" + k + " j=" + j);

    if (j < k || k < 0)

        return 0; 

    if (k <= j - k)

        return jCk_helper(j, k);

    else

        return jCk_helper(j, j - k);

}  

}