using System;

public class Program

{

    public static void Main()

    {

        saya saya1 = new anak();

        int c = saya1.a() + (saya1 as cucu).b();

        Console.WriteLine(c);

    }

}

class saya

    {

    public virtual int a()

        {return 1;}

}

class anak:saya

    {

    public override int a() {return 2;}

    public virtual int b() {return 3;}

    }

class cucu:anak

    {

    public override int b(){return 4;}

}