升序插入之后有多高

把 13、15、17、23、24 按升序依次插入。运行下面这段程序：

class BNode:
    def __init__(self, val):
        self.val = val
        self.left = None
        self.right = None

def insert(root, val):
    if root is None:
        return BNode(val)
    if val < root.val:
        root.left = insert(root.left, val)
    elif val > root.val:
        root.right = insert(root.right, val)
    return root

def height(node):
    if node is None:
        return 0
    a = height(node.left)
    b = height(node.right)
    return 1 + (a if a > b else b)

root = None
for v in [13, 15, 17, 23, 24]:
    root = insert(root, v)
print(height(root))