using System;

​

public class Program

{

    public class Base

    {

        public virtual void hello()

        {

        }

    }

​

    //

    public class Parent_1 : Base

    {

        public override void hello()

        {

            Console.WriteLine("Hi 1");

        }

    }

​

    public class Parent_2 : Parent_1

    {

        public override void hello()

        {

            base.hello();

            Console.WriteLine("Hi 2");

        }

    }

​

    public static void Main()

    {

        Parent_1 p = new Parent_2();

        p.hello();

    }

}