MOD = 10 ** 9 + 7

n = int(input())
alst = list(map(int, input().split()))
ans = 0
times = pow(3, n - 2, MOD)
inv3 = pow(3, MOD - 2, MOD)
tmp = 1
for a in alst[:-1]:
    tmp *= a
    tmp %= MOD
    ans += tmp * 2 * times
    ans %= MOD
    times *= inv3
    times %= MOD
ans += tmp * alst[-1]
print(ans % MOD)