using System;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            QuackTheQuacker(new Toy());
            QuackTheQuacker(new Duck());
        }

        static void QuackTheQuacker(dynamic quacker)
        {
            quacker.Quack();
        }
    }

    class Toy
    {
        public void Quack()
        {
            Console.WriteLine("A toy that quacks");
        }
    }

    class Duck
    {
        public void Quack()
        {
            Console.WriteLine("A duck that quacks");
        }
    }
}