N = 10**6
mod = 998244353
fac = [1]*(N+1)
finv = [1]*(N+1)
for i in range(N):
    fac[i+1] = fac[i] * (i+1) % mod
finv[-1] = pow(fac[-1], mod-2, mod)
for i in reversed(range(N)):
    finv[i] = finv[i+1] * (i+1) % mod

def cmb1(n, r, mod):
    if r <0 or r > n:
        return 0
    r = min(r, n-r)
    return fac[n] * finv[r] * finv[n-r] % mod

p = 2
C = [[0]*(p+1) for i in range(p+1)] #C[n][k] > nCk

for i in range(p+1):
    for j in range(i+1):
        if j == 0 or j == i:
            C[i][j] = 1
        else:
            C[i][j] = C[i-1][j-1]+C[i-1][j]

def cmb2(n, k, p):
    ret = 1
    while n > 0:
        ni = n%p
        ki = k%p
        ret *= C[ni][ki]
        ret %= p
        n //= p
        k //= p
    return ret

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

x = 0
o = 0
e = 0
for i, b in enumerate(B):
    if b != -1:
        if cmb2(n-1, i, 2)%2 == 1:
            x ^= b
    else:
        if cmb2(n-1, i, 2)%2 == 1:
            o += 1
        else:
            e += 1

ans = 0
if x == 0:
    for k in range(o+1):
        if k%2 == 0:
            continue
        ans += cmb1(o, k, mod)*pow(2, e, mod)
        ans %= mod
else:
    for k in range(o+1):
        if k%2 == 1:
            continue
        ans += cmb1(o, k, mod)*pow(2, e, mod)
        ans %= mod
print(ans)