MOD = 10 ** 9 + 7
N = int(input())
A = list(map(int,input().split()))
ans = 0
tmp = 1
for i in range(N):
    a = A[i]
    tmp *= a
    tmp %= MOD
    if i < N - 1:
        ans += tmp * 2 * pow(3,N - 2 - i,MOD)
    else:
        ans += tmp
    ans %= MOD

print(ans)