#include<bits/stdc++.h>

using namespace std;
using ll = long long int;
using lc = complex<double>;

int main(void) {
    constexpr ll MOD = 1e9+7;
    constexpr double PI = acos(-1);
    cout << fixed << setprecision(32);
    cin.tie(0); ios::sync_with_stdio(false);

    ll n;
    cin >> n;
    vector<ll> a(n);
    for(auto &e: a) cin >> e;

    ll r = 1;
    bool ng = false;
    for(ll i=0; i<n; i++) {
        if(a[i] == 0) {
            cout << -1 << endl;
            return 0;
        }
        if(a[i] == 1) r *= 1;
        if(a[i] == 2) r *= 4;
        if(a[i] == 3) r *= 729;
        if(a[i] >3 || r > MOD) {
            ng = true;
        }
    }
    if(ng) {
        cout << MOD << endl;
        return 0;
    }
    cout << ((r) ? (MOD % r) : -1) << endl;
    return 0;
}