n = int(input())
a = [int(i) for i in input().split()]

mod = 10**9+7

ans = 0
ans += a[0]*(2*pow(3, n-2, mod))%mod
ans %= mod
kk = a[0]

for i in range(1,n):
    kk *= a[i]
    kk %= mod
    if i == n-1:
        ans += kk
        ans %= mod
        break
    ans += kk*(2*pow(3,n-i-2,mod))
    ans %= mod
    
print(ans)