class Horse {
  void talk() {
    System.out.println("Howdy!");
  }
}

class Unicorn extends Horse {
  void talk() {
    System.out.println("Bonjour...");
  }
}

class Story {
  public static void main(String[] args) {
    Horse a = new Horse();
    double m = 3.4;
    a.talk();
    Unicorn b = new Unicorn();
    b.talk();
    Horse c;
    c = new Unicorn();
    c.talk();
    Unicorn d = new Horse(); // doesn't work!
  }
}