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

C = [0]*n
C[0] = A[0]
for i in range(1, n):
    C[i] = C[i-1]*A[i]
    C[i] %= mod

N = 10**6
P = [0]*N
P[0] = 1
for i in range(1, N):
    P[i] = P[i-1]*3
    P[i] %= mod
ans = 0
for i in range(n-1):
    ans += C[i]*2*P[n-2-i]
    ans %= mod
ans += C[-1]
ans %= mod
print(ans)