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

const ll mod = 1000000007;

int main() {
    int N;
    cin >> N;
    ll A[N];
    bool flag0 = false;
    bool flag4 = false;
    for (int i = 0; i < N; i++) {
        cin >> A[i];
        if (A[i] == 0) flag0 = true;
        if (A[i] >= 4) flag4 = true;
    }
    if (flag0) {
        cout << "-1\n";
        return 0;
    }
    if (flag4) {
        cout << mod << "\n";
        return 0;
    }
    ll ans = 1;
    int cnt = 0;
    ll b[4] = {1, 4, 729};
    for (int i = 0; i < N; i++) {
        ans *= b[A[i] - 1];
        if (ans > mod) break;
    }
    cout << (mod % ans) << "\n";
    return 0;
}