def max_height(node):
    """
    Binary Tree max height
    Complexity: O(NODES)

    Find height with DFS.
    """
    if node is None:
        return 0
    else:
        left_height = max_height(node.left)
        right_height = max_height(node.right)

        if left_height > right_height:
            return left_height+1
        else:
            return right_height+1