using System;

​

public class Tree

{

public virtual void Info()

{

Console.WriteLine("дърво");

}

}               

    public class Apple: Tree

    {

    public override void Info()

    {

    Console.WriteLine("ябълка");

    }

    }

    public class Cherry: Tree

    {

    public override void Info()

    {

    Console.WriteLine("череша");

    }

    }

public class Program

{

    public static void Main(string[] args)

    {

        /* Tree t = new Tree();

        Apple a = new Apple();

        t = a;

        t.Info();

        Cherry c = new Cherry();

        t = c;

        t.Info(); 

        */

        // nagore proizvoden -> bazov

    /*  Apple a = new Apple();

        Tree t = a ;

        t.Info();

        */

        //nadolu bazov -> proizvoden

        /* Tree t = new Apple();

        Apple a = (Apple) t ;

        a.Info();

        */

        //1 nachin

        /*Tree t = new Apple();

        if (t is Apple)

        {

        Console.WriteLine("Yes");

            t.Info();

        }

        else Console.WriteLine("No");

        */

        //2 nachin

        Tree t = new Apple();

        if ( t as Apple != null )           

        {

        Console.WriteLine("Yes");

            t.Info();

        }

        else Console.WriteLine("No");

    }

}