# -*- coding:utf-8 -*-
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    def TreeDepth(self, pRoot):
        # write code here
        if not pRoot: return 0
        queue=[pRoot]
        node=pRoot
        count=0
        while queue:
            nodes=[]
            while queue:
                node=queue.pop()
                #print(out)
                if node.right:nodes.append(node.right)
                if node.left:nodes.append(node.left)
            count+=1
            queue=nodes
        return count