"""

最初の掛け算の項以外は、対消滅する

"""

import sys
from sys import stdin

mod = 10**9+7

N = int(stdin.readline())

A = list(map(int,stdin.readline().split()))

ans = 0

now = 1
for i in range(N):

    now *= A[i]
    now %= mod

    if i == N-1:
        ans += now
    else:
        ans += now * 2 * pow(3,N-2-i)

print (ans % mod)