public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        TreeMap<Integer, List<String>> map = new TreeMap<>();

        int N = scanner.nextInt();

        for (int i = 0; i < N; i++) {
            int index = scanner.nextInt();
            String s = scanner.next();
            s = i < N / 2 ? "-" : s;
            if (map.containsKey(index)) {
                map.get(index).add(s);
            } else {
                List<String> list = new ArrayList<>();
                list.add(s);
                map.put(index, list);
            }
        }

        String answer = map.values().stream().flatMap(Collection::stream)
                .reduce("", String::concat);


        System.out.println(answer);
    }