#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair<ll,ll> P;
typedef vector<ll> VI;
typedef vector<VI> VVI;
#define REP(i,n) for(ll i=0;i<(n);i++)
#define ALL(v) v.begin(),v.end()
template<typename T> bool chmax(T &x, const T &y) {return (x<y)?(x=y,true):false;};
template<typename T> bool chmin(T &x, const T &y) {return (x>y)?(x=y,true):false;};
constexpr ll MOD=1000000007;
constexpr ll INF=2e18;

ll power(ll x, ll y){
    x%=MOD;
    ll ret=1;
    while(y){
        if(y&1) ret=ret*x%MOD;
        x=x*x%MOD;
        y>>=1;
    }
    return ret;
}

int main(){
    int n; cin >> n;
    VI a(n); REP(i,n) cin >> a[i];
    ll ans=0, x=1;
    REP(i,n){
        x=x*a[i]%MOD;
        if(i==n-1)
            ans=(ans+x)%MOD;
        else
            ans=(ans+x*power(3,n-i-2)*2%MOD)%MOD;
    }
    cout << ans << endl;
}