import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
sys.setrecursionlimit(10**7)
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################

n = ni()
a = na()
ans = 0
mod = 10**9+7
c = 1
for i in range(n):
    c*=a[i]
    c%=mod
    if i==n-1:
        ans+=c
    else:
        ans+=2*pow(3,n-i-2,mod)*c
    ans%=mod
print(ans)