MOD = 998244353

n = int(input())
b = list(map(int, input().split()))

mask = n - 1
sum_fixed = 0
k = 0
m = 0

for i in range(1, n+1):
    if ((i-1) & mask) == (i-1):
        if b[i-1] == -1:
            k += 1
        else:
            sum_fixed += b[i-1]
    else:
        if b[i-1] == -1:
            m += 1

sum_fixed %= 2

if k == 0:
    if sum_fixed == 1:
        print(pow(2, m, MOD))
    else:
        print(0)
else:
    exponent = (k - 1) + m
    print(pow(2, exponent, MOD))