#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int(i) = 0; (i) < (n); (i)++)
#define FOR(i, m, n) for(int(i) = (m); (i) < (n); (i)++)
#define All(v) (v).begin(), (v).end()
#define pb push_back
#define MP(a, b) make_pair((a), (b))
template <class T> vector<T> make_vec(size_t a, T val) {
    return vector<T>(a, val);
}
template <class... Ts> auto make_vec(size_t a, Ts... ts) {
    return vector<decltype(make_vec(ts...))>(a, make_vec(ts...));
}
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using Graph = vector<vector<int>>;
template <typename T> struct edge {
    int to;
    T cost;
    edge(int t, T c) : to(t), cost(c) {}
};
template <typename T> using WGraph = vector<vector<edge<T>>>;
const int INF = 1 << 30;
const ll LINF = 1LL << 60;
const int MOD = 1e9 + 7;

int main() {
    int N;
    cin >> N;
    ll res = 1LL;
    vector<ll> A(N);
    rep(i, N) cin >> A[i];
    sort(All(A));
    if(A[0] == 0) {
        cout << -1 << endl;
        return 0;
    }
    rep(i, N) {
        if(A[i] == 1) {
            res *= 1;
        } else if(A[i] == 2) {
            res *= 4;
        } else if(A[i] == 3) {
            res *= 729;
        } else {
            cout << MOD << endl;
            return 0;
        }
        if(res > MOD) {
            cout << MOD << endl;
            return 0;
        }
    }
    cout << MOD % (res) << endl;
}