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