using System;

public class Program

{

    public static void Main()

    {

        int num = 0, factorial = 1;

        Console.Write("Enter a number: ");

        int.TryParse(Console.ReadLine(), out num);

        for (int i = num; i > 0; i--) {

            factorial *= i;

        }

        Console.WriteLine("\n" + num + "! = " +factorial);

    }

}