查 23 比了几次

还是那棵树（17、24、15、13、23 依次插入）。运行下面这段程序，它数的是"比了几次"：

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

cur = build()
n = 0
while cur is not None:
    n += 1
    if 23 == cur.val:
        break
    cur = cur.left if 23 < cur.val else cur.right
print(n)