#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, cnt = 0, x, i;
  scanf("%d", &n);
  while (n--) {
    scanf("%d", &x);
    if (x == 1) cnt++;
  }
  if (cnt)
    cout << -1 << endl;
  else
    cout << 1 << endl;
  return 0;
}
