using System;

​

public class Program

{

    public static void Main(string[] args)

    {

        Console.WriteLine("Welcome to my first program!");

        int n, j;

        Console.Write("Enter any number you like below");

        n = Convert.ToInt16(Console.ReadLine());

/*      if(n%2==0)

        {

            Console.WriteLine("So ban vua nhap la so chan");

        }else

        {

            Console.WriteLine("So ban vua nhap la so le");

        }

        while(n!=3)

        {

            Console.Write("Enter again! ");

            n = Convert.ToInt16(Console.ReadLine());

        }

        Console.WriteLine("Ban vua nhap dung so 3");

        */

        if(n%2==0) j=2;

        else j=2;

        int S=1;

        for(int i=j; j<=n; j=j+2)

        {

            S = S*j;

        }

        Console.WriteLine("Ket qua la : " + S);

    }

}