// #include <atcoder/all>
#include <bits/stdc++.h>
#define FOR(i, a, n) for(ll i = (ll)a; i < (ll)n; i++)
#define FORR(i, n) for(ll i = (ll)n - 1LL; i >= 0LL; i--)
#define rep(i, n) FOR(i, 0, n)
#define ALL(x) begin(x), end(x)
using namespace std;
using ll = long long;
constexpr ll Mod = 998244353;
constexpr ll mod = 1e9 + 7;
constexpr ll inf = 1LL << 60;
const double PI = acos(-1);
template <typename T1, typename T2> inline bool chmax(T1 &a, T2 b) {
    return a < b && (a = b, true);
}
template <typename T1, typename T2> inline bool chmin(T1 &a, T2 b) {
    return a > b && (a = b, true);
}
/*-------------------------------------------*/

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

    int n;
    cin >> n;
    vector<int> a(n);

    ll x = 1;

    rep(i, n) {
        cin >> a[i];
        if(x >= mod) continue;
        if(a[i] == 1)
            x *= 1;
        else if(a[i] == 2)
            x *= 4;
        else if(a[i] == 3)
            x *= 729;
    }

    if(*min_element(ALL(a)) == 0) {
        cout << -1 << endl;
        return 0;
    }
    if(*max_element(ALL(a)) >= 4) {
        cout << mod << endl;
        return 0;
    }
    cout << mod % x << endl;

    return 0;
}