#include <bits/stdc++.h>

using namespace std;

#define rep(i, n) for(int i = 0; i < (int)n; ++i)
#define FOR(i, a, b) for(int i = a; i < (int)b; ++i)
#define rrep(i, n) for(int i = ((int)n - 1); i >= 0; --i)

using ll = long long;
using ld = long double;

const int Inf = 1e9;
const double EPS = 1e-9;
const int MOD = 1e9 + 7;

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(0);
    int n;
    cin >> n;
    priority_queue<string, vector<string>, greater<string> > pq;
    rep (i, n) {
        string s;
        cin >> s;
        s += '~';
        pq.push(s);
    }
    while (!pq.empty()) {
        string s = pq.top();
        pq.pop();
        cout << s[0];
        if (s.size() <= 2) continue;
        pq.push(s.substr(1));
    }
    cout << endl;
    
    return 0;
}