import std;

int readInt() {
	int x;
	readf!" %d"(x);
	return x;
}

const long P = (1e9 + 7).to!long;
long qpow(long a, long b, long m = P) {
	long r = 1 % P, t = a % P;
	for(; b; b /= 2) {
		if(b & 1)
			r = r * t % P;
		t = t * t % P;
	}
	return r;
}

void main() {
	int n = readInt;
	auto a = new int[](n).map!(i => readInt);
	
	long ans = 0, mul = 1;
	foreach(i; 0 .. n) {
		mul = mul * a[i] % P;
		if(i + 1 < n) {
			ans += mul * 2 * qpow(3, n - i - 2) % P;
		} else {
			ans += mul;
		}
		ans %= P;
	}
	writeln(ans);
}