#include <iostream>

using lint = long long;
constexpr lint MOD = 1000000007;

void solve() {
    int n;
    std::cin >> n;

    lint prod = 1;
    while (n--) {
        lint x;
        std::cin >> x;

        if (x == 0) {
            prod = 0;
            break;
        } else if (prod <= MOD && x <= 3) {
            switch (x) {
                case 2:
                    prod *= 4;
                    break;
                case 3:
                    prod *= 729;
                    break;
            }
        } else {
            prod = MOD + 1;
        }
        prod = std::min(prod, MOD + 1);
    }

    std::cout << (prod == 0 ? -1 : MOD % prod) << "\n";
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}