using System;

using System.Linq;

using System.IO;

​

interface Welcoming {

    public void welcome() {

      Console.WriteLine("welcome");

    }

}

​

class A : Welcoming {

    public void welcome() {

      Console.WriteLine("welcome2");

    }

}

​

class B : Welcoming { }

​

public class Program {

    public static void Main() {

        Welcoming instanceA = new A();

        Welcoming instanceB = new B();

        instanceA.welcome();

        instanceB.welcome();

    }

}

​

​