using System;

public class Program

{

    public static void Main()

    {

        Middle x = new Child();

        Console.WriteLine(x.f(1));

    }

    public class Base

    {

        public virtual string f(int a){

            return "base";

        }

    }

    public class Middle : Base

    {

        public new string f(int a){

            return "middle";

        }

    }

    public class Child : Middle

    {

        public new string f(int a){

            return "child";

        }

    }

}