#include <bits/stdc++.h>
using namespace std;


#define ll long long
#define rep(i, n) for (int i = 0; i < (n); i++)
#define P pair<int, int>

ll memo[4] = {0, 1, 4, 729};

const ll MOD = 10e8 + 7;
int main() {
  ll n;
  cin >> n;

  ll ans = 1;

  rep(i, n) {
    int a;
    cin >> a;

    if (a >= 4) {
      cout << MOD << endl;
      return 0;
    } 

    if (a == 0) {
      cout << -1 << endl;
      return 0;
    }

    ans *= memo[a];

    if (ans > MOD) {
      cout << MOD << endl;
      return 0;
    }
  }

  cout << (MOD % ans ? (MOD % ans) : -1) << endl;

}