class Element:
    def __str__(self):
        return self.__class__.__name__

    def __add__(self, other):
        key = tuple(sorted((str(self), str(other))))
        if key in transformation_table:
            return type(transformation_table[key], (Element, ), {})
        return None


class Water(Element):
    pass


class Air(Element):
    pass


class Fire(Element):
    pass


# key-tuple's strings should be sorted in alphabetical order
transformation_table = {
    ("Air", "Water"): "Storm",
    ("Fire", "Water"): "Vapor",
    ("Dirt", "Water"): "Mud",
    ("Air", "Fire"): "Lightning",
    ("Air", "Dirt"): "Dust",
    ("Dirt", "Fire"): "Lava",
}

print(Water() + Air())