#define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define RT return
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;

int R[4] = { 0,1, 4, 729 };

void solve() {
    const int P = (int)1e9 + 7;

    int N;
    cin >> N;
    vi A(N);
    rep(i, N) {
        cin >> A[i];
        if (A[i] == 0) {
            cout << -1 << endl;
            return;
        }
    }

    ll S = 1;
    rep(i, N) {
        if (A[i] > 3 || (S *= R[A[i]]) > P) {
            cout << P << endl;
            return;
        }
    }
    cout << P % S << endl;

}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(15);
    solve();
    return 0;
}