#include <bits/stdc++.h>
#define INF 1000000001LL
#define MOD 1000000007LL
#define long long long
#define all(x) x.begin(),x.end()
using namespace std;

int main()
{
	ios_base::sync_with_stdio(0); 
    cin.tie(0);

	int n;
	cin >> n;
	vector<int> arr(n);
	long res = 1;
	for(int i = 0; i<n; i++)
	{
		cin >> arr[i];

		if(arr[i] == 0)
		{
			cout << -1 << endl;
			return 0;
		}

		if(arr[i] > 3)
			res = MOD+1;
		if(arr[i] == 3)
			res*=729;
		if(arr[i] == 2)
			res*=2;
		res = min(MOD+1,res);
	}
	cout << MOD%res << endl;
	
    return 0;
}