N = int(input())
B = list(map(int,input().split()))
P = 998244353

power = [0] * N
i = 2
while i < N:
    for j in range(1,(N-1)//i + 1):
        power[i*j] += 1
    i *= 2
now = 0
count1 = 0
count2 = 0
S = 0
if B[0] == -1:
    count1 += 1
else:
    S += B[0]
if B[N-1] == -1:
    count1 += 1
else:
    S += B[0]
    
for i in range(1,N-1):
    now = now + power[N-i] - power[i]
    if now > 0:
        if B[i] == -1:count2 += 1
    else:
        if B[i] == -1:count1 += 1
        else:S += B[i]
if count1 == 0 and S % 2 == 0:
    print(0)
    exit()
if count1 == 0:u = count2
else:u = count1 + count2 -1

u = count1 + count2 - 1
t = 1
for _ in range(u):
    t *= 2
    t %= P
print(t)