using System;

​

public class Program

{

    public static void Main()

    {

        int num = 4;

        int result = Fact(num);

        Console.WriteLine(result);

    }

​

    static int Fact(int num)

    {

        int result = 1;

        for (int i = 1; i <= num; i++)

        {

            result *= i;

        }

​

        return result;

    }

}