#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <set>
#include <map>
#define N_MAX 200002

using namespace std;
typedef long long ll;


ll fac[N_MAX];

void init(ll MOD){
    fac[0]=1;fac[1]=1;
    for(int i=2;i<N_MAX;i++){
        fac[i]=fac[i-1]*(ll)i;
        fac[i] %= MOD;
    }
}

template <typename T>
T pow(T a, ll n, ll MOD) {
	T ans = 1;
	T tmp = a;
	for (int i = 0; i <= 60; i++) {
		ll m = (ll)1 << i;
		if (m & n) {
		ans *= tmp;
		ans %= MOD;
		}
		tmp *= tmp;
		tmp %= MOD;
	}
	return ans;
}

const ll p = 1000000007;

int N;
ll A[200000];

ll c[4] = {1, 1, 4, 729};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    cin >> N;
    bool too_big = false;
    bool contain_zero = false;
    for(int i = 0; i < N; i++) {
        cin >> A[i];
        if(A[i] == 0) contain_zero = true;
        if(A[i] >= 4) too_big = true;
    }
    if(contain_zero){
        cout << -1 << endl;
        return 0;
    }
    if(too_big){
        cout << p << endl;
        return 0;
    }
    ll ans = 1;
    for(int i = 0; i < N; i++){
        ans *= c[A[i]];
        if(ans > p){
            cout << p << endl;
            return 0;
        }
    }
    cout << p%ans << endl;
}