#include <bits/stdc++.h>
using namespace std;

int main() {
    const int x[4] = { 0, 1, 4, 729 };
    int n;
    cin >> n;
    vector<int> a(n);
    bool big = false;
    for (int i = 0; i < n; i++) {
        cin >> a[i];
        if (a[i] == 0) {
            cout << -1 << endl;
            return 0;
        }
        if (a[i] >= 4) {
            big = true;
        }
    }
    if (big) {
        cout << 1000000007 << endl;
        return 0;
    }
    int64_t p = 1;
    for (int i = 0; i < n; i++) {
        p *= x[a[i]];
        if (p >= 1000000007) {
            cout << 1000000007 << endl;
        }
    }
    cout << 1000000007 % p << endl;
}