#include <bits/stdc++.h>

using namespace std;
void fast_io() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
}

int main() {
    fast_io();
    int n;
    cin >> n;
    vector<string> s(n);
    for (int i = 0; i < n; i++) {
        cin >> s[i];
        s[i] += 'z' + 1;
    }
    priority_queue<string, vector<string>, greater<>> pq(s.begin(), s.end());
    string ans = "";
    while (!pq.empty()) {
        string t = pq.top();
        pq.pop();
        reverse(t.begin(), t.end());
        ans += t.back();
        t.pop_back();
        reverse(t.begin(), t.end());
        if (t.size() > 1) {
            pq.push(t);
        }
    }
    cout << ans << endl;
}