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

md = 1000000007

ret, prod = 0, 1
d23 = 2 * pow(3, md - 2, md) % md

for i, a in enumerate(A):
    ret = ret * 3 % md
    if prod:
        prod *= a  # mod をとっていない
        ret += prod * (d23 if i < N - 1 else 1) % md

print(ret % md)