#include <bits/stdc++.h>
using namespace std;

bool isp(long n) {
  if (n < 2) return false;
  long s = __builtin_ctzl(n - 1), d = n >> s;
  for (auto b : {2, 325, 9375, 28178, 450775, 9780504, 1795265022}) {
    long p = 1, i = s, j = d, k = b;
    while (j > 0) {
      if (j & 1) p = (__int128) p * k % n;
      k = (__int128) k * k % n;
      j >>= 1;
    }
    while (p != 1 && p != n - 1 && b % n && i--) p = (__int128) p * p % n;
    if (p != n - 1 && i != s) return false;
  }
  return true;
}

int main() {
  int N;
  cin >> N;
  vector<string> A(N);
  for (int i = 0; i < N; i++) cin >> A.at(i);
  vector<long> V;
  sort(A.begin(), A.end());
  do {
    string tmp;
    for (auto a : A) tmp += a;
    V.push_back(stol(tmp));
  } while (next_permutation(A.begin(), A.end()));
  sort(V.rbegin(), V.rend());
  for (auto v : V) if (isp(v)) return cout << v << "\n", 0;
  cout << -1 << "\n";
}