public static void main(String[] args) throws IOException {
        try (BufferedReader reader = new BufferedReader(new FileReader("bstsimple.in"));
             PrintStream stream = new PrintStream("bstsimple.out")) {

            System.setOut(stream);

            BinarySearchTree tree = new BinarySearchTree();

            String str;
            while ((str = reader.readLine()) != null) {
                String[] s = str.split(" ");
                switch (s[0]) {
                    case "insert":
                        if (!tree.exists(Integer.parseInt(s[1])))
                            tree.insert(Integer.parseInt(s[1]));
                        break;
                    case "delete":
                        tree.delete(Integer.parseInt(s[1]));
                        break;
                    case "exists":
                        System.out.println(tree.exists(Integer.parseInt(s[1])));
                        break;
                    case "next":
                        Integer n = tree.next(Integer.parseInt(s[1]));
                        System.out.println(n == null ? "none" : n);
                        break;
                    case "prev":
                        Integer nn = tree.prev(Integer.parseInt(s[1]));
                        System.out.println(nn == null ? "none" : nn);
                        break;
                }
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }