using System;

​

​

public interface IGroup<T> {

}

​

​

​

public class Member {

    IGroup<Member> group;

    public Member(IGroup<Member> gr) {

        this.group = gr;

    }

}

​

public class Group : IGroup<Member> {

    public Group() {

        new Member(this);

    }

}

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

}