import sys
input = sys.stdin.readline
N = int(input())
a = list(map(int, input().split()))
mod = 10 ** 9 + 7

res = 0
cs = 1
for i in range(N):
  x = a[i]
  cs *= x
  cs %= mod
  res += cs * (2 * pow(3, max(0, N - i - 2), mod)) ** (i < N - 1)
  res %= mod
print(res)