#include <algorithm>
#include <cmath>
#include <cstdio>
#include <functional>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
using namespace std;
using ll = long long;
int main() {
  ll limit = 1000000007;
  int n;
  cin >> n;
  ll num = 1;
  for(int i = 0; i < n; i++) {
    ll tmp, a;
    cin >> a;
    if(a < 2) {
      continue;
    }
    tmp = a;
    while(tmp--) {
      for(int j = 0; j < tmp + 1; j++) {
        num *= a;
        if(num > limit) {
          cout << limit << '\n';
          return 0;
        }
      }
    }
  }
  if(limit % num == 0) {
    cout << -1 << '\n';
  } else {
    cout << limit % num << '\n';
  }
  return 0;
}