#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1000000007;
int main(){
  int N;
  cin >> N;
  vector<int> A(N);
  for (int i = 0; i < N; i++){
    cin >> A[i];
  }
  bool zero = false;
  for (int i = 0; i < N; i++){
    if (A[i] == 0){
      zero = true;
    }
  }
  if (zero){
    cout << -1 << endl;
  } else {
    bool big = false;
    long long ans = 1;
    for (int i = 0; i < N; i++){
      if (A[i] >= 4){
        big = true;
        break;
      } else {
        if (A[i] == 2){
          ans *= 4;
        }
        if (A[i] == 3){
          ans *= 729;
        }
        if (ans > MOD){
          big = true;
          break;
        }
      }
    }
    if (big){
      cout << MOD << endl;
    } else {
      cout << MOD % ans << endl;
    }
  }
}