using System;
using System.Numerics;
//Write a program that calculates N!/K! for given N and K (1<K<N).

class Program
{
static void Main()
{
    Console.Write("Enter a number for factorial !N [N > K > 1]: ");
    int n = int.Parse(Console.ReadLine());
    Console.Write("Enter a number for factorial !K: ");
    int k = int.Parse(Console.ReadLine());
    BigInteger sumK = 1;
    BigInteger sumN = 1;
    if (n > k & n >= 0)
    {
        Console.Write("!{0}", n);
        while (n >= 1)
        {
            sumN *= n;
            n--;

        }
        Console.WriteLine(" = {1}", n, sumN);
        Console.Write("!{0}", k);

        while (k >= 1)
        {
            sumK *= k;
            k--;

        }
        Console.WriteLine(" = {1}", k, sumK);
        Console.WriteLine("[!N/!K]: {0}/{1} = {2}", sumN, sumK, sumN / sumK);
    }
    else
    {
        Console.WriteLine("Invalid Input !");
    }
}
}