class BSTNode:
    def __init__(self, data):
        self.data = data
        self.left = None
        self.right = None

def kiritish(root, data):
    if root is None:
        return BSTNode(data)
    if data < root.data:
        root.left = kiritish(root.left, data)
    elif data > root.data:
        root.right = kiritish(root.right, data)
    return root

root = None
for son in [10, 5, 15, 3, 7]:
    root = kiritish(root, son)

def chop_etish(node):
    if node is None:
        return
    chap = node.left.data if node.left else "-"
    ong = node.right.data if node.right else "-"
    print(f"{node.data} | chap: {chap}, o'ng: {ong}")
    chop_etish(node.left)
    chop_etish(node.right)

chop_etish(root)

10 | chap: 5, o'ng: 15
5 | chap: 3, o'ng: 7
3 | chap: —, o'ng: —
7 | chap: —, o'ng: —
15 | chap: —, o'ng: —

# 10 → root bo'ldi
# 5:  5 < 10 → chapga
# 15: 15 > 10 → o'ngga
# 3:  3 < 10 → chapga; 3 < 5 → yanada chapga
# 7:  7 < 10 → chapga; 7 > 5 → o'ngga