using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

}

​

public abstract class TestClass1

{

}

​

public class TestClass2 : TestClass1

{

    protected TestClass2 (string a)

    {

    }

}

​

public class TestClass3 : TestClass2

{

    protected TestClass3() : base (string.Empty)

    {

    }

}