N = int(input())
B = list(map(int, input().split()))
mod = 998244353
odd, even, zero_or_one = 0, 0, 0
for i in range(N):
    if (N - 1) & i == i:
        if B[i] == -1:
            odd += 1
        elif B[i] == 1:
            zero_or_one ^= 1
    else:
        if B[i] == -1:
            even += 1

if odd:
    print(pow(2, even + odd - 1, mod))
else:
    if zero_or_one:
        print(pow(2, even, mod))
    else:
        print(0)