#include<bits/stdc++.h>
using namespace std;

#define all(v) v.begin(),v.end()
using ll = long long;
using ull = unsigned long long;
using vll=vector<ll>;
ll mod=1e9+7;

int main(){
    ll N;
    cin>>N;
    vll A(N);
    for(int i=0;i<N;i++){
        cin>>A[i];
        if(A[i]>=4){
            cout << mod << endl;
            return 0;
        }
        if(A[i]==0){
            cout << -1 << endl;
            return 0;
        }
    }
    ll ans=1;
    for(int i=0;i<N;i++){
        if(A[i]==2) ans*=4;
        if(A[i]==3) ans*=27*27;
        if(ans>mod){
            cout << mod << endl;
            return 0;
        }
    }
    cout << mod%ans << endl;
}