package qualification;

import java.util.*;
import java.util.stream.Collectors;

public class B {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int k = in.nextInt();
        HashMap<String, Integer> map = new HashMap<>();
        List<String> strings = new ArrayList<>();
        int total = (int) (Math.pow(2, k) - 1);
        in.nextLine();
        for (int i = 0; i < total; i++) {
            strings.add(Arrays.stream(in.nextLine().split(" ")).sorted(String::compareTo).reduce((a, b) -> a + " " + b).get());
        }

        if (strings.size() != new HashSet<>(strings).size()) {
            System.out.println("NO SOLUTION");
            return;
        }

        for (int i = 0; i < total; i++) {
            String[] s = strings.get(i).split(" ");
            map.put(s[0], map.getOrDefault(s[0], 0) + 1);
            map.put(s[1], map.getOrDefault(s[1], 0) + 1);
        }
        if (map.keySet().size() != total + 1) {
            System.out.println("NO SOLUTION");
            return;
        }
        boolean res = true;
        int count = (total + 1) / 2;
        for (int i = 0; i < k; i++) {
            int finalI = i;
            if (i != k - 1) {
                res = res && map.values().stream().filter(q -> q == finalI + 1).count() == count;
            } else {
                res = res && map.values().stream().filter(q -> q == finalI + 1).count() == count * 2;
            }
            count /= 2;
        }
        if (res) {
            List<String> finalists = map.keySet().stream().filter(q -> map.get(q) == k - 1).collect(Collectors.toList());
            System.out.println(finalists.get(0) + " " + finalists.get(1));
        } else {
            System.out.println("NO SOLUTION");
        }
    }
}