using System;

public class Program

{

    public static void Main()

    {

        int n;

        int k;

        do

        {

            Console.WriteLine("Enter n: ");

            n = int.Parse(Console.ReadLine());

            Console.WriteLine("Enter k: ");

            k = int.Parse(Console.ReadLine());

        } while (k < n);

        int denom = 1;

        for (int i = n + 1; i <= k; i++)

        {

            denom *= i;

        }

        double result = 1.0 / denom;

        Console.WriteLine("The result is {0}", result);

    }

}