#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("YES");}else{puts("NO");}
#define MAX_N 200005

int main() {
    ll n; cin >> n;
    ll a[n] = {};
    rep(i,n) cin >> a[i];

    rep(i,n){
        if(a[i] == 0){
            cout << -1 << endl;
            return 0;
        }
    }

    ll mul = 1;
    const ll MOD = 1000000007;
    rep(i,n){
        if(a[i] >= 4){
            cout << MOD << endl;
            return 0;
        }
        if(a[i] == 1){
            continue;
        }
        if(a[i] == 2){
            mul *= 4;
        }
        if(a[i] == 3){
            mul *= 729;
        }
        if(mul > MOD){
            cout << MOD << endl;
            return 0;
        }
    }

    ll ans = MOD % mul;
    cout << ans << endl;
    return 0;
}