using System;

public class Program

{

    public static void Main()

    {

        var ab = new AB();

        ab.Run();

        ab.Walk();

    }

    public class A<T> where T : class {

        private static Lazy<int> lazyClient = new Lazy<int>(InitClient);

        protected static int client => lazyClient.Value;

        static A() {

            Console.WriteLine("Hello World A");

        }

        public void Run() {

            Console.WriteLine("Run Run");

        }

        private static int InitClient()

        {

            // Perform any initialization here

            Console.WriteLine("Init Client 3");

            return 3;

        }

    }

    public class AB : A<B> {

        static AB() {

            Console.WriteLine("Hello World B");

        }

        public void Walk() {

            Console.WriteLine("Walk" + client);

        }

    }

    public class B {

    }

    public class C {

    }

}