MOD = 998244353

n = int(input())
B = list(map(int, input().split()))
bi = 0
x = 0
odd = 0
even = 0
for i in range(n):
    if B[i] == -1:
        if bi == 0:
            odd += 1
        else:
            even += 1
    else:
        if bi == 0:
            x ^= B[i]
    if i == n - 1:
        break
    y = n - i - 1
    while y % 2 == 0:
        y //= 2
        bi += 1
    y = i + 1
    while y % 2 == 0:
        y //= 2
        bi -= 1

if odd > 0:
    print(pow(2, odd + even - 1, MOD))
elif x == 0:
    print(0)
else:
    print(pow(2, even, MOD))