using System;

public class Program

{

    public int factorial(int n) {

        int r=1;

        if (n>1){

            return r=n*factorial(n-1);

        }else{ 

            return 1;

        }

    }

    public static void Main()

    {

        Program p=new Program();

        Console.WriteLine(p.factorial(5));

    }

}