#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define pii pair<long long,long long>
#define pll pair<long long, long long>
#define rep(i,l,r) for(long long i = l;i<r;i++)

#define SSTR( x ) static_cast< std::ostringstream & >( \
        ( std::ostringstream() << std::dec << x ) ).str()

#define fastout  ios_base::sync_with_stdio(false);cin.tie(NULL);
using namespace std;
using namespace __gnu_pbds;

typedef tree<pll,null_type,less<pll>,rb_tree_tag,tree_order_statistics_node_update> order_set;

const long long INF = (long long)1e9 + 7;
const long long LLINF = (long long)1e18 + 7;

mt19937 mt('O' + '4' + 'K' + 'O');

void kekek()
{

    mt();
    #ifdef EB_UG
        freopen("in.txt", "r", stdin), freopen("out.txt", "w", stdout);
    #endif
    #ifndef EB_UG
        ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    #endif
}

struct match {
    string s1;
    int ind1;
    string s2;
    int ind2;
};

map<string, int> indx;
map<int, int> cnt;

int main() {
    kekek();
    int n;
    cin >> n;
    vector<match> turik(n);
    set<string> heh;
    for (int i = 0; i < n; i++) {
        cin >> turik[i].s1;
        cin >> turik[i].s2;
        heh.insert(turik[i].s1);
        heh.insert(turik[i].s2);
    }
    vector<string> peps;
    for (auto it: heh) {
        peps.push_back(it);
    }
    int pn = peps.size();
    for (int i = 0; i < pn; i++) {
        indx[peps[i]] = i;
    }
    for (auto &it: turik) {
        it.ind1 = indx[it.s1];
        it.ind2 = indx[it.s2];
    }
    for (auto it: turik) {
        cnt[indx[it.s1]]++;
        cnt[indx[it.s2]]++;
    }
    int need = (n + 1) >> 1;
            vector<bool> used(n + 10);
    vector<vector<int>> total(1000);


    int ind = 0;
    while(true) {
        if (need == 1)
            need *= 2;
        int mn = INF;
        for(auto it: cnt) {
            if (it.second == 0)
                continue;
            mn = min(mn, it.second);
        }
        if (mn == INF)
            break;
        vector<int> prek;
        for (auto it: cnt) {
            if (it.second == mn) {
                prek.push_back(it.first);
            }
        }
        if (prek.size() != need) {
            cout << "NO SOLUTION";
            return 0;
        }

        vector<int> del;
        for (int i = 0; i < n; i++) {
            if (used[i])
                continue;
            if (cnt[turik[i].ind1] == 1 || cnt[turik[i].ind2] == 1) {
                used[i] = true;
                del.push_back(i);
            }
        }
        for (auto it: del) {
                cnt[turik[it].ind1] = max(cnt[turik[it].ind1] - 1, 0);
                cnt[turik[it].ind2] = max(cnt[turik[it].ind2] - 1, 0);
        }
        total[ind] = prek;
        ind++;
        need >>= 1;
    }
    for (auto it: total[ind - 2]) {
        cout << peps[it] << ' ';
    }
}