#include <bits/stdc++.h>
using namespace std;
bool less_vectors(const vector<long long>& a, const vector<long long>& b) {
  return a.size() < b.size();
}
struct Comparator {
  bool operator()(const std::pair<long long, long long>& lhs,
                  const std::pair<long long, long long>& rhs) const {
    if (lhs.first != rhs.first)
      return lhs.first < rhs.first;
    else
      return lhs.second < rhs.second;
  }
};
long long fastexpo(long long a, long long b) {
  long long res = 1;
  while (b > 0) {
    if (b % 2 == 1) res = ((res) % 1000000009 * (a) % 1000000009) % 1000000009;
    a = ((a) % 1000000009 * (a) % 1000000009) % 1000000009;
    b /= 2;
  }
  return res;
}
long long fastexpom(long long a, long long b, long long m) {
  long long res = 1;
  while (b > 0) {
    if (b % 2 == 1) res = (((res) % m) * ((a) % m)) % m;
    a = (((a) % m) * ((a) % m)) % m;
    b /= 2;
  }
  return res;
}
long long modinv(long long a, long long m = 1000000009) {
  return fastexpom(a, m - 2, m);
}
bool comp(string s1, string s2) { return s1 + s2 < s2 + s1; }
int32_t main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  long long n;
  cin >> n;
  vector<string> v(n);
  for (long long i = 0; i < n; i++) cin >> v[i];
  sort(v.begin(), v.end(), comp);
  for (long long i = 0; i < n; i++) cout << v[i];
  return 0;
}
