#include <bits/stdc++.h>
using namespace std;
const int N = 2100000;
const long long mod = 1e9 + 7;
int power(int a, int p) {
  int r = 1, y = a;
  while (p) {
    if (p & 1) r = (1LL * r * y) % mod;
    p >>= 1;
    y = (1LL * y * y) % mod;
  }
  return r;
}
int ara[N];
bool comp(string a, string b) {
  string temp = a + b;
  string tt = b + a;
  if (temp < tt) {
    return 1;
  } else
    return 0;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  int n;
  cin >> n;
  vector<string> v;
  for (int i = 0; i < n; i++) {
    string s;
    cin >> s;
    v.push_back(s);
  }
  sort(v.begin(), v.end(), comp);
  for (auto x : v) cout << x;
  cout << endl;
}
