//#include <atcoder/all>
#include <bits/stdc++.h>
#include <cmath>
using namespace std;
//using namespace atcoder;
using ll = long long;
#define all(A) A.begin(),A.end()
using vll = vector<ll>;
#define rep(i, n) for (long long i = 0; i < (long long)(n); i++)
using Graph = vector<vector<ll>>;
Graph G;
vll E;
vector<bool> seen;

int main() {
	ll N;
	cin>>N;
	vll A(N);
	rep(i,N){
		cin>>A[i];
		if(A[i]==0){
			cout<<-1<<endl;
			return 0;
		}
		
	}
	rep(i,N){
		if(A[i]>3){
			cout<<ll(1e9+7)<<endl;
			return 0;
		}
	}
	ll an=1;
	rep(i,N){
		if(A[i]==1){
			
		}

		else if(A[i]==2){
			an*=2;
		}
		else{
			an*=729;
		}
		if(an>1e9+7){
			cout<<ll(1e9+7)<<endl;
			return 0;
		}
	}
	cout<<ll(1e9+7)%an<<endl;
}