from collections.abc import Iterable


def accum_dp(xs: Iterable, f, op, e, init: dict, *, is_reset=True):
    dp = init.copy()
    for x in xs:
        pp = {} if is_reset else dp.copy()
        dp, pp = pp, dp
        for fm_key, fm_val in pp.items():
            for to_key, to_val in f(fm_key, fm_val, x):
                dp[to_key] = op(dp.get(to_key, e), to_val)

    return dp


def op(a, b):
    return a + b


ans = 0


def f(k, v, x):
    global ans
    t, b = k  # (取った, 0を含むか)

    if t == 0:
        yield k, v
        # 取る
        nb = b | (x == 0)
        yield (1, nb), v
    elif t == 1:
        nb = b | (x == 0)
        yield (1, nb), v

        if b:
            ans += v
    else:
        assert False


N = int(input())
A = list(map(int, input().split()))

init = {(0, False): 1}
dp = accum_dp(A, f, op, 0, init)
for (t, b), v in dp.items():
    if t == 1 and b:
        ans += v

print(ans)