private void inOrder(TreeNode root) {

		if (root != null) {
			inOrder(root.left);
			if (root.val < prev.val) {
				if (first == null) {
					first = prev;
					second = root;
				} else {
					second = root;
					return; // will TLE if not return here
				}
			}
			prev = root;
			inOrder(root.right);
		}
	}