#include <bits/stdc++.h>
using namespace std;
long long x_pow_y(long long x, long long y) {
  if (y == 0) return 1;
  long long temp;
  temp = x_pow_y(x, y / 2);
  if (y % 2 == 0)
    return (temp * temp);
  else
    return (x * (temp * temp));
}
long long binarySearch(vector<long long>& arr, long long t) {
  long long n = arr.size();
  long long i = 0, j = n - 1;
  while (i <= j) {
    long long mid = (i + j) / 2;
    if (t == arr[mid]) return mid;
    if (t < arr[mid])
      j = mid - 1;
    else
      i = mid + 1;
  }
  return -1;
}
long long min(long x, long y, long z) { return min(x, min(y, z)); }
bool cmp(string a, string b) {
  string x = a + b;
  string y = b + a;
  return x < y;
}
vector<string> v;
int main() {
  long long i, j;
  ios_base ::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  long long n;
  cin >> n;
  string s;
  for (i = 0; i < n; i++) {
    cin >> s;
    v.push_back(s);
  }
  sort(v.begin(), v.end(), cmp);
  for (i = 0; i < v.size(); i++) cout << v[i];
  cout << "\n";
  return 0;
}
