using System;

public class Program

{   

    public static int factorialUsingRecursion(int number){

        if(number==0){

            return 1;

        }

        return number*factorialUsingRecursion(number-1);

    }

    public static void Main()

    {

        int number = Convert.ToInt32(Console.ReadLine());

        int factorial = factorialUsingRecursion(number);

        Console.WriteLine(factorial);

    }

}