public class Test {

    private static class Pair {
        public int index;
        public String value;

        public Pair(int index, String value) {
            this.index = index;
            this.value = value;
        }
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        List<Pair> list = new ArrayList<>();

        int N = scanner.nextInt();

        for (int i = 0; i < N; i++) {
            int index = scanner.nextInt();
            String s = scanner.next();
            list.add(new Pair(index, i < N / 2 ? "-" : s));
        }


        String answer = list.stream()
                .sorted(Comparator.comparingInt(pair -> pair.index))
                .map(pair -> pair.value)
                .reduce("", String::concat);

        System.out.println(answer);
    }
}