#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) {
    int a;
    cin >> a;
    if (a == 1) {
      cout << -1 << endl;
      return 0;
    }
  }
  cout << 1 << endl;
  return 0;
}
