mod = 10**9+7
n, *A = map(int, open(0).read().split())
ans = 0
t = 1
for i in range(n):
    t = t*A[i]%mod
    if i < n-1:
        ans += t * 2 * pow(3, n-2-i)
    else:
        ans += t
    ans %= mod
print(ans)