typedef long long ll;
typedef long double ld;
#include <bits/stdc++.h>
using namespace std;
#define int long long

long long modpow(long long a, long long n, long long mod) {
    long long res = 1;
    while (n > 0) {
        if (n & 1) res = res * a % mod;
        a = a * a % mod;
        n >>= 1;
    }
    return res;
}
const ll MOD = 1e9+7;
signed main(){
    ll n;
    std::cin >> n;
    vector<ll> a(n);
    ll now = 1;
    ll ans = 0;
    for (int i = 0; i < n; i++) {
        std::cin >> a[i];
        now *= a[i];
        now %= MOD;
        ans += now*modpow(3,max(0ll,n-2-i),MOD)%MOD*(2*(i<n-1)+1*(i>=n-1))%MOD;
        ans %= MOD;
        // std::cout << ans << std::endl;
    }
    std::cout << ans << std::endl;
}