using System;

​

public interface IGreenery

{

    IGreenery WaterIt();

    string Message();

}

​

public class Tree : IGreenery

{

    public IGreenery WaterIt()

    {

        return this;

    }

    public string Message() {   

        return "tree";

    }

}

​

public class GinkoTree : IGreenery

{

    public IGreenery WaterIt()

    {

        return this;

    }

    public string Message() {   

        return "GinkoTree";

    }

}

​

public class Program

{

    public static void Main()

    {

        var tree = new Tree();

        var ginko = new GinkoTree();

        Console.WriteLine(tree.WaterIt().Message());

        Console.WriteLine(ginko.WaterIt().Message());

    }

}