def insert(node, val):
    # 1. Normal BST insert
    if not node: return Node(val)
    if val < node.val:
        node.left = insert(node.left, val)
    elif val > node.val:
        node.right = insert(node.right, val)
    else: return node  # duplicate

    # 2. Update height
    node.h = 1 + max(height(node.left),
                     height(node.right))

    # 3. Check balance
    b = balance_factor(node)

    # LL case
    if b > 1 and val < node.left.val:
        return rotate_right(node)
    # RR case
    if b < -1 and val > node.right.val:
        return rotate_left(node)
    # LR case
    if b > 1 and val > node.left.val:
        node.left = rotate_left(node.left)
        return rotate_right(node)
    # RL case
    if b < -1 and val < node.right.val:
        node.right = rotate_right(node.right)
        return rotate_left(node)

    return node