#include <iostream>
using namespace std;
int main(){
    int n;cin>>n;
    long long r = 1;
    long long A[3] = {1,4,729}; 
    for(int i = 0; n > i; i++){
        int x;cin>>x;
        if(x >= 4){
            cout << 1000000007 << endl;
            return 0;
        }else if(x == 0){
            cout << -1 << endl;
            return 0;
        }
        r *= A[x-1];
        if(r > 1000000007){
            cout << 1000000007 << endl;
            return 0;
        }
    }
    cout << 1000000007%r << endl;
}