using System;

public class Program

{

    public static void Main()

    {

        R recv = new R();

        new S().send( recv, new M());

        new S().send( recv, new N());

        new X().send( recv, new N());

        new X().send( recv, new M());

    }

}

​

    public class M{}

    public class N{}

    public class R

    {

        public void accept( S sender, M message){}

        public void accept( X sender, N message){}

    }

​

​

public class S

{

    public void send( R receiver, M message )

    {

        receiver.accept(this, message);

    }

}

​

public class X

{

    public void send( R receiver, N message )

    {

        receiver.accept(this, message);

    }

}