from sys import stdin
n, *a = map(int, stdin.read().split())
p = 10 ** 9 + 7

pow3 = [1 for i in range(n)]
for i in range(1,n):
    pow3[i] = pow3[i-1] * 3 % p

ans = 0
prod = 1
for i in range(n):
    prod = prod * a[i] % p
    if i < n - 1:
        ans = (ans + prod * 2 * pow3[n-i-2] % p) % p
    else:
        ans = (ans + prod) % p

print("{}".format(ans))