N = int(input())
l = list(map(int, input().split()))
md = 1000000007

prod = []
p = 1
for i in range(N):
	p = (p*l[i]) % md
	prod.append(p)

ans = 0
for i in range(N-1):
	ans += (2 * 3**(N-i-2) * prod[i]) % md

ans += prod[N-1]

print(ans%md)