/* -*- coding: utf-8 -*-
 *
 * 1237.cc:  No.1237 EXP Multiple! - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 200000;
const int MOD = 1000000007;

/* typedef */

typedef long long ll;

/* global variables */

int as[MAX_N], fs[4];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);

  for (int i = 0; i < n; i++) {
    scanf("%d", as + i);
    if (as[i] == 0) {
      puts("-1");
      return 0;
    }
  }

  fs[0] = 0, fs[1] = 1, fs[2] = 4, fs[3] = 729;

  ll p = 1;
  for (int i = 0; i < n; i++) {
    if (as[i] > 3 || p * fs[as[i]] > MOD) {
      printf("%d\n", MOD);
      return 0;
    }
    p *= fs[as[i]];
  }

  printf("%lld\n", MOD % p);
  return 0;
}