#include <bits/stdc++.h>
#define be(v) (v).begin(),(v).end()
#define pb(q) push_back(q)
#define rep(i, n) for(int i=0;i<n;i++)
#define all(i, v) for(auto& i : v)
typedef long long ll;
using namespace std;
const ll mod=1000000007, INF=(1LL<<60);
#define doublecout(a) cout<<fixed<<setprecision(10)<<a<<endl;
#define asdf() cout << "debugdayo!!" << endl;

int main() {
    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(false);
    ll n;
    cin >> n;
    bool ok = false, ok0 = 0;
    vector<ll> a(n);
    rep(i, n){
        cin >> a[i];
        if(a[i] == 0) ok0 = true;
    }
    if(ok0) {
        cout << -1 << endl;
        return 0;
    }
    ll ans = 1;
    rep(i, n){
        if(a[i] == 2){
            ans *= 4;
        }else if(a[i] == 3){
            ans *= 9*9*9;
        }else if(a[i] >= 4){
            ok = true;
        }
        if(ans > mod) ok = true;
        if(ok){
            cout << mod << endl;
            return 0;
        }
    }
    cout << mod % ans << endl;


    return 0;
}