#include <bits/stdc++.h>
//#include<atcoder/all>
using namespace std;
//using namespace atcoder;
using ll = long long;
#define all(A) A.begin(),A.end()
using vll = vector<ll>;
#define rep(i, n) for (long long i = 0; i < (long long)(n); i++)

ll mod = 1e9+7;

int main() {
   ll N;
   cin>>N;
   ll an=0;
   vll T(N+1,1);
   rep(i,N)T[i+1]=(T[i]*3)%mod;
   ll S=1;
   rep(i,N-1){
       ll A;
       cin>>A;
       S*=A;
       S%=mod;
       an+=S*2*T[N-i-2];
       an%=mod;
   }
   ll A;
   cin>>A;
   S*=A;
   an+=S;
   cout<<an%mod<<endl;
}