/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public int maxDepth(TreeNode root) {


        if( root == null )
            return 0;
        if( root.left == null && root.right == null)
            return 1;
        if( root.left == null)
            return maxDepth(root.right)+1;
        if( root.right == null)
            return maxDepth(root.left)+1;
        return Math.max(maxDepth(root.left),maxDepth(root.right))+1;
    }

   
}