def main() -> None:
    N = int(input())
    A = list(map(int, input().split()))

    res = 0
    cuprod = 1
    mod = 10**9 + 7

    for i in range(N):
        cuprod *= A[i]
        cuprod %= mod

        diff: int

        if N - 2 - i >= 0:
            diff = cuprod * 2 * pow(3, N - 2 - i, mod)
        else:
            diff = cuprod

        res += diff
        res %= mod

    print(res)

if __name__ == '__main__':
    main()