#include <bits/stdc++.h>
using namespace std;
vector<pair<string, int> > v;
string s[100005];
int main() {
  int N;
  scanf("%d", &N);
  for (int i = 0; i < N; i++) {
    cin >> s[i];
    int len = s[i].length();
    int t = 60 - s[i].length();
    while (t >= s[i].length()) {
      t -= s[i].length();
      s[i] += s[i];
    }
    s[i] += s[i].substr(0, t);
    v.push_back(pair<string, int>(s[i], len));
  }
  sort(v.begin(), v.end());
  for (int i = 0; i < v.size(); i++) {
    for (int j = 0; j < v[i].second; j++) printf("%c", (v[i].first)[j]);
  }
  return 0;
}
