#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];
        reverse(s[i].begin(), s[i].end());
    }
    string ans = "";
    while (true) {
        bool non_empty = false;
        int mi_idx = -1;
        for (int i = 0; i < n; i++) {
            if (!s[i].empty()) {
                if (!non_empty || s[i].back() < s[mi_idx].back()) {
                    mi_idx = i;
                }
                non_empty = true;
            }
        }
        if (!non_empty) {
            break;
        }
        ans += s[mi_idx].back();
        s[mi_idx].pop_back();
    }
    cout << ans << endl;
}