mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

    N = int(input())
    A = list(map(int, input().split()))

    cur = 1
    ans = 0
    for i, a in enumerate(A):
        cur = (cur * a)%mod
        if i != N-1:
            ans = (ans + (cur * 2 * pow(3, N-2-i, mod))%mod)%mod
        else:
            ans = (ans + cur)%mod
    print(ans)


if __name__ == '__main__':
    main()