using System;
using System.Collections.Generic;

/*
public class TreeNode
{
    public int val;
    public TreeNode left;
    public TreeNode right;

    public TreeNode (int x)
    {
        val = x;
    }
}
*/

class Solution {
    /**
     * 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
     * @return int整型
     */
    public int maxDepth (TreeNode root) {
        // write code here
        if (root == null)
            return 0;
        int nLLen = maxDepth(root.left);
        int nRLen = maxDepth(root.right);
        return 1 + Math.Max(nLLen, nRLen);
    }
}