#include <bits/stdc++.h>
using namespace std;
const long long mod = 1000000007;
long double pi = 3.14159265358979323846264338327950;
long double e = 2.7182818284590452353602874713527;
vector<string> v;
bool comp(string &s1, string &s2) {
  string ab = s1 + s2, ba = s2 + s1;
  return ab < ba;
}
int main() {
  ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) {
    string s;
    cin >> s;
    v.push_back(s);
  }
  sort(v.begin(), v.end(), comp);
  for (int i = 0; i < ((int)(v).size()); i++) cout << v[i];
  return 0;
}
