N = int(input())
mod = 10**9+7
ans = 0
now = 1
for i, a in enumerate(map(int, input().split())):
    now *= a
    now %= mod
    if i == N-1:
        ans += now
        continue
    ans += now * pow(3, N-i-2, mod) * 2
    ans %= mod
print(ans)