#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll MOD = 1000000007;
using P = pair<int,int>;
#define rep(i, n) for(int i = 0; i < n; i++)
#define all(x) (x).begin(),(x).end()

int main(){
    int n;
    cin >> n;
    vector<ll> a(n);
    ll x = 1, k = 2;
    rep(i,n){
        ll p;
        cin >> p;
        x = x * p % MOD;
        a[i] = x;
    }
    ll ans = a[n-1];
    rep(i,n-1){
        ans = (ans + a[n-i-2] * k) % MOD;
        k = k * 3 % MOD;
    }
    cout << ans << endl;
    return 0;
}