#include<iostream>
#include<vector>
using namespace std;

int main(){
    long ans = 0;
    long N; cin >> N;
    long P = 1;
    long C;
    vector<long> b(N, 1);
    b[N - 2] = 2; for(long i = N - 3; i >= 0; i--) {b[i] = b[i + 1] * 3; b[i] %= (long)1e9+7;}
    for(long i = 0; i < N; i++){
        cin >> C;
        P *= C; P %= (long)1e9+7;
        ans += P * b[i]; ans %= (long)1e9+7;
    }
    ans %= (long)1e9+7;
    cout << ans << endl;
}