using System;

public class Program

{

    public static void Main()

    {

        int n = 0;

        int fact = 1;

        Console.WriteLine("Please enter number: ");

        n = Convert.ToInt32(Console.ReadLine());

        while (n > 1) {

            fact = fact * n;

            n = n - 1;

        }

        Console.WriteLine(fact);

    }

}