using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public class A {}

    public class B : A {}

    public class C {}

    public static void Main()

    {

        IEnumerable<A> result = new object [] { new A(), new B(), new C() }.OfType<A>();

        Console.WriteLine(result.Count());

    }

}