#include <algorithm>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <vector>
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rrep(i, n) for (int i = (n)-1; i >= 0; i--)
using namespace std;
typedef long long int lli;
lli MOD = 1000000007;
int main()
{
    priority_queue<pair<string, int>, vector<pair<string, int>>, greater<pair<string, int>>> que;
    int n;
    cin >> n;
    string s[55] = {};
    int cnt[55] = {};
    int size[55] = {};
    rep(i, n)
    {
        cin >> s[i];
        cnt[i] = 1;
        size[i] = s[i].size();
        s[i] += "zzzzzzz";
        que.push(make_pair(s[i], i));
    }
    string t = "";
    while (!que.empty()) {
        t += que.top().first[0];
        int id = que.top().second;
        //        cout << id << ' ' << t << endl;
        que.pop();
        if (cnt[id] < size[id]) {
            que.push(make_pair(s[id].substr(cnt[id], s[id].size() - cnt[id]), id));
            cnt[id]++;
        }
    }
    cout << t << endl;
}