#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int t;
  t = 1;
  while (t--) {
    long long n, a[1001];
    cin >> n;
    for (int i = 0; i <= n - 1; i++) {
      cin >> a[i];
    }
    sort(a, a + n);
    if (a[0] == 1)
      cout << -1;
    else
      cout << 1;
  }
  cerr << "Time taken : " << (float)clock() / CLOCKS_PER_SEC << " secs" << endl;
  return 0;
}
