using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        Child x  = new Child(null);

    }

    public class TestBase{

        public TestBase(string message)

        {

            Console.WriteLine("Base class");

        }   

    }

    public class Child:TestBase{

        public Child(ComplexObject x)   :base(x.x.ToString())

        {

        }

    }

    public class ComplexObject{

        public int x = 12;

    }

}