Implement an Animal class with a constructor that takes a parameter for the animal's name and has an instance method speak that returns a string like "Spot says hello!".

Implement a Dog class that inherits from Animal and uses the inherited constructor but changes the speak method to return a string like "Spot barks!".

Implement a Cat class that inherits from Animal and uses the inherited constructor but changes the speak method to return a string like "Spot meows!".

Outside the function, create instances of the Animal, Dog, and Cat classes, call their speak methods, and print the result.