public static Node lca(Node root, int v1, int v2) {
        if (root == null)
            return null;
        Set<Node> set = new HashSet<>();
        set.add(root);
        Node node = root;
        while (node.data != v1) {
            node = v1 < node.data ? node.left : node.right;
            set.add(node);
        }
        set.add(node);
        Node n = root;
        node = root;
        while (set.contains(node)) {
            n = node;
            node = v2 < node.data ? node.left : node.right;
        }
        return n;
    }