using System;

public class Program

{

    public static void Main()

    {

        int num = 0;

        Console.WriteLine("Factorials!");

        string ans = Console.ReadLine();

        num = Convert.ToInt32(ans);

        Console.WriteLine(enemy.Num(num));

​

    }

    public abstract class enemy

    {

    public static int Num(int num)

    {

        if (num == 0){return 1;}

        else{return (num * (num-1));}

    }

}

}