def get_height_max(self, A):
        if A == None:
            return 0

        if A.left == A.right == None:
            return 1

        left_height_max = 1 + self.get_height_max(A.left)
        right_height_max = 1 + self.get_height_max(A.right)

        return max(left_height, right_height)