# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
#
# 代码中的类名、方法名、参数名已经指定,请勿修改,直接返回方法规定的值即可
#
# 
# @param root TreeNode类 
# @param o1 int整型 
# @param o2 int整型 
# @return int整型
#
class Solution:
    def lowestCommonAncestor(self , root: TreeNode, o1: int, o2: int) -> int:
        # write code here
        # root 为None 或者等于其中一个节点
        def  dfs(root,o1,o2)->int:
            if not root:  # 如果节点是None  由于树上节点的值是1  1<=n<=10^5
                return  0
            if  root.val==o1 or root.val ==o2:
                return root.val
            left =self.lowestCommonAncestor(root.left,o1,o2)
            right =self.lowestCommonAncestor(root.right,o1,o2)

            if  left==0:
                return right
            if  right==0:
                return left
            return root.val
        return dfs(root,o1,o2)