/*
 * C# Program to Calculate the Value of nCr
 */
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApplication
{
class Program
{
    static void Main(string[] args)
    {
        int n, r,per,fact,fact1,fact2;
        Console.WriteLine("Enter the Value of 'n' and 'r' to find the Permutation :");
        n = Convert.ToInt32(Console.ReadLine());
        r = Convert.ToInt32(Console.ReadLine());
        fact = n;
        for (int i = n - 1; i >= 1; i--)
            {
                fact = fact * i;
            }
        fact2 = r;
        for (int i = r - 1; i >= 1; i--)
            {
                fact2 = fact2 * i;
            }
        int number;
        number = n - r;
        fact1 = number;
        for (int i = number - 1; i >= 1; i--)
            {
                fact1 = fact1 * i;
            }
        fact1 = fact2 * fact1;
        per = fact / fact1;
        Console.WriteLine("Combination : {0}",per);
        Console.ReadLine();
    }
}
}

/*
Enter the value of 'n' and 'r' to find the Permutation :
10
5
Combination : 252