using System;

public class Program

{

    public delegate void D();

    public static void Main()

    {

        D print = PrintHello;

        print();

        print = PrintGoodbye;

        print();

    }

    public static void PrintHello()

    {

        Console.WriteLine("Hello"); 

    }

    public static void PrintGoodbye()

    {

        Console.WriteLine("Goodbye");   

    }

}