import sys
input = lambda: sys.stdin.readline().rstrip()

mod = 10**9 + 7

#  -----------------------  #

n = int(input())
A = list(map(int, input().split()))

ans = 0
mul = 1
for i,a in enumerate(A):
  mul *= a
  mul %= mod
  if i == n-1:
    continue
  ans += mul * 2 * pow(3, max(0,n-i-2), mod)
  ans %= mod
ans += mul
ans %= mod
print(ans)