import java.lang.*;
import java.util.*;
import node.*;

class MaxDepthOfTree {
	public static int maxDepth(TreeNode root) {
		if (root.left == null || root.right == null)
			return 1;
		int l = maxDepth(root.left) + 1;
		int r = maxDepth(root.right) + 1;
		return l > r ? l : r;
	}

	public static void main(String[] args) {
		TreeNode leftLeaf = new TreeNode(9);
		TreeNode middleLeaf = new TreeNode(15);
		TreeNode rightLeaf = new TreeNode(7);
		TreeNode parent = new TreeNode(20, middleLeaf, rightLeaf);
		TreeNode root = new TreeNode(3, leftLeaf, parent);
		System.out.println(maxDepth(root));
	}
}