using System;

using System.Numerics;                  

public class Program

{

     static void Main()

    {

         BigInteger factorial = 1;

         Console.WriteLine("Въведи N: ");

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

         int temp = n;

         do

         {

             factorial *= n;

             n--;

         }while (n > 0);

         Console.WriteLine(temp + "! = " + factorial);

         Console.ReadKey();

    }

}