#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int arr[n + 1];
  for (int i = 0; i < n; i++) cin >> arr[i];
  for (int i = 0; i < n; i++) {
    if (arr[i] == 1) {
      cout << "-1";
      return 0;
    }
  }
  cout << "1";
  return 0;
}
