mod = 10**9 + 7
N = int(input())
A = list(map(int,input().split()))
inv_3 = pow(3,mod-2,mod)
ans = 0
tmp = 2*pow(3,N-2,mod)*A[0]
ans += tmp
ans %= mod

for i in range(1,N):
    tmp *= A[i]
    if i < N-1:
        tmp *= inv_3
    else:
        tmp *= pow(2,mod-2,mod)
    tmp %= mod
    ans += tmp
    ans %= mod
print(ans)