#include <bits/stdc++.h>
using namespace std;
long long read() {
  long long a = 0, b = getchar(), c = 1;
  while (!isdigit(b)) c = b == '-' ? -1 : 1, b = getchar();
  while (isdigit(b)) a = a * 10 + b - '0', b = getchar();
  return a * c;
}
int n;
string s[50005];
bool cmp(string a, string b) { return (a + b) < (b + a); }
int main() {
  n = read();
  for (int i = 0; i < n; i++) cin >> s[i];
  sort(s, s + n, cmp);
  for (int i = 0; i < n; i++) cout << s[i];
  return 0;
}
