# Duck typing

class Duck():
    def __init__(self, x):
        self.x = x

    def quack(self):
        return 42

    def walk(self):
        return "Walking in Memphis"

class Dog():
    def __init__(self, x):
        self.x = x

    def bark(self):
        # it's a silent breed
        return None

    def walk(self):
        return "Get the stick! Get the stick!"


def f(obj):
    a = obj.walk()
    return [a, a, a]

# Glavni program
print(f(Duck(17))) # dela
print(f(Dog(1))) # dela
# print(f("cow")) # dela