using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DerivedClass
{
    class Program
    {
        static void Main(string[] args)
        {
            AbstractClass d1 = new DerivedA();
            DerivedA d2 = new DerivedA();

            Console.WriteLine(d1 is AbstractClass);
            Console.WriteLine(d2 is AbstractClass);
            Console.WriteLine(d1 is DerivedA);
            Console.WriteLine(d2 is DerivedA);
        }
    }
}