MOD = 10**9+7
N = int(input())
A = list(map(int,input().split()))
ans = 0
c = pow(3,N-1,MOD)
a = 1
for i in range(N-1):
    a = (a*A[i])%MOD
    c = c*pow(3,MOD-2,MOD)%MOD
    ans = (ans +2*c*a)%MOD
ans = (ans+a*A[N-1])%MOD
print(ans)