#include <algorithm>

struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode() : val(0), left(nullptr), right(nullptr) {}
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
    TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
};

class Solution {
	public:
		int maxDepth(TreeNode* root) {
			if (!root)
				return (0);
			return (std::max(maxDepth(root->left), maxDepth(root->right)) + 1);
		}
	};
