class Mammal:   
    der walk(self):   
    print('walking')   
   
   
class Dog(Mammal):   
    def bark(self)   
	print('barking')   
   
class Cat(Mammal):   
    def be_annoying(self)   
	print('annoying')   
   
   
dog1 = Dog()   
dog1.walk()   
dog1.bark()   
   
cat1 = Cat()   
cat1.be_annoying()