n = int(input())
a = list(map(int,input().split()))
mod = 10**9+7

ans = 0

# 全て*の場合を先に加算
num1 = 1
for i in range(n):
    num1 *= a[i]
    num1 %= mod
ans += num1

for i in range(n-1):
    if i == 0:
        former = a[i]
        tmp = 2*pow(3,n-i-2,mod)
        tmp %= mod
        ans += former*tmp
        ans %= mod
    else:
        former *= a[i]
        tmp = 2*pow(3,n-i-2,mod)
        tmp %= mod
        former %= mod
        ans += former*tmp
        ans %= mod

print(ans)