class A:
    def g(self, n):
        return n + 1

    def f(self, m):
        return self.g(m)

class B(A):
    def g(self, n):
        return 2 * n

if __name__ == "__main__":
    b = B()
    print(b.f(2))
    a = A()
    print(a.f(2))