#include <bits/stdc++.h>

#define rep(i, n) for (int (i) = 0; (i) < (int)(n); (i)++)

const int dx[] = {1, 0, -1, 0};
const int dy[] = {0, 1, 0, -1};
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef pair<int, int> pii;

string S[55];
int cur[55];

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N;
    cin >> N;
    int all = 0;
    for (int i = 0; i < N; i++) {
        cin >> S[i];
        all += S[i].size();
    }
    string T;
    string last;
    for (int i = 0; i < 50; i++) last += "z";
    while (1) {
        if (T.size() == all) break;
        vector<pair<string, int> > words;
        for (int i = 0; i < N; i++) {
            if (cur[i] == S[i].size()) continue;
            words.push_back(make_pair(S[i].substr(cur[i])+last, i));
        }
        sort(words.begin(), words.end());
        cur[words[0].second]++;
        T += words[0].first.substr(0, 1);
    }
    cout << T << endl;
    return 0;
}