#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    int N; cin >> N;
    ll target = 1e9+7;
    vector<int> A(N);
    rep(i,N) cin >> A[i];

    if(*min_element(A.begin(), A.end()) == 0) {
        cout << -1 << endl;
    }
    else if(*max_element(A.begin(), A.end()) >= 4) {
        cout << target << endl;
    } else {
        ll prod = 1;
        rep(i,N) {
            if(A[i] == 2) {
                prod *= 4;
                if(prod > target) { cout << target << endl; return 0; }
            }
            if(A[i] == 3) {
                prod *= 729;
                if(prod > target){ cout << target << endl; return 0; }
            }
        }
        cout << (target % prod) << endl;
    }
}