#include "bits/stdc++.h"

#define int long long

using namespace std;
using ll = long long;
using P = pair<ll, ll>;
//const ll INF = (1LL << 61);
ll mod = 1000000007;


struct mint {
	ll x; // typedef long long ll;
	mint(ll x = 0) :x((x%mod + mod) % mod) {}
	mint operator-() const { return mint(-x); }
	mint& operator+=(const mint a) {
		if ((x += a.x) >= mod) x -= mod;
		return *this;
	}
	mint& operator-=(const mint a) {
		if ((x += mod - a.x) >= mod) x -= mod;
		return *this;
	}
	mint& operator*=(const mint a) {
		(x *= a.x) %= mod;
		return *this;
	}
	mint operator+(const mint a) const {
		mint res(*this);
		return res += a;
	}
	mint operator-(const mint a) const {
		mint res(*this);
		return res -= a;
	}
	mint operator*(const mint a) const {
		mint res(*this);
		return res *= a;
	}
	mint pow(ll t) const {
		if (!t) return 1;
		mint a = pow(t >> 1);
		a *= a;
		if (t & 1) a *= *this;
		return a;
	}

	// for prime mod
	mint inv() const {
		return pow(mod - 2);
	}
	mint& operator/=(const mint a) {
		return (*this) *= a.inv();
	}
	mint operator/(const mint a) const {
		mint res(*this);
		return res /= a;
	}
};
istream& operator>>(istream& is, mint& a) { return is >> a.x; }
ostream& operator<<(ostream& os, const mint& a) { return os << a.x; }
signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	int N; cin >> N;
	vector<int>A(N); for (int i = 0; i < N; i++)cin >> A[i];
	mint now = 1;
	mint ans = 0;
	for (int i = 0; i < N - 1; i++) {
		now *= A[i];
		ans += now * mint(3).pow(N - i - 2) * 2;
	}
	now *= A[N - 1]; ans += now;
	cout << ans << endl;
	return 0;
}