# Demonstrating runtime polymorphism through method overriding

class Animal:
    def speak(self):
        return "Some sound"


class Bird(Animal):
    def speak(self):      
        return "Tweet"
    
class Dog(Animal):
    def speak(self):
        return "Woof"   
    

print(Animal().speak())  # Some sound
print(Bird().speak())    # Tweet
print(Dog().speak())     # Woof