public class Solution {
    public static List<Pair> result = new LinkedList<>();
    public static StringBuilder builder;
    public static String[] array;
    public static Set<String> set = new TreeSet<>();
    public static List<String> list = new ArrayList<>();

    public static void main(String[] args) throws IOException {
        String reverse;
        builder = new StringBuilder();
        String fileName;
        try (BufferedReader reader = new BufferedReader(new InputStreamReader(System.in))) {
            fileName = reader.readLine();
        }

        try (BufferedReader bufferedReader = new BufferedReader(new FileReader(fileName))) {
            while (bufferedReader.ready()) {
                builder.append(bufferedReader.readLine() + " ");
            }
        }

        array = builder.toString().split(" ");

        for (String s : array)
            list.add(s);

        for (String s : list) {
            Pair pair = new Pair();
            if (set.contains(s))
                continue;
            builder = new StringBuilder(s);
            reverse = builder.reverse().toString();

            if (s.equals(reverse)) {
                if (list.indexOf(s) != list.lastIndexOf(s)) {
                    pair.first = s;
                    pair.second = s;
                    result.add(pair);
                    set.add(s);
                }
            }

            else {
                if (list.contains(reverse)) {
                    pair.first = s;
                    pair.second = reverse;
                    result.add(pair);
                    set.add(s);
                    set.add(reverse);
                }
            }
        }

        //for (Pair p : result) {
        //    System.out.println(p.first + " " + p.second);
        //}
    }