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


def ord2(n):
    i = 0
    while not n % 2:
        i += 1
        n >>= 1
    return i


comb = [0]*N
for i in range(1, N):
    comb[i] = comb[i-1]+ord2(N-i)-ord2(i)

cta = 0
ctb = 0
v = 0
for i in range(N):
    if not comb[i]:
        if B[i] == -1:
            cta += 1
        else:
            v ^= B[i]
    else:
        if B[i] == -1:
            ctb += 1

if v == cta == 0:
    print(0)
else:
    print(pow(2, ctb+max(0, cta-1), MOD))