#include <bits/stdc++.h>
using namespace std;
int c, a, i, n;
int main() {
  cin >> n;
  for (i = 0; i < n; i++) {
    cin >> a;
    if (i == 0)
      c = a;
    else
      c = min(c, a);
  }
  if (c == 1)
    cout << -1;
  else
    cout << 1;
}
