md = 998244353;
N = int(input())
A = list(map(int, input().split()))
kai = [1] * (N+1)
fkai = [1] * (N + 1)
for i in range(1, N+1) :
	kai[i] = kai[i - 1] * i
	kai[i] %= md
fkai[N] = pow(kai[N], -1, md);
for i in range(N, 0, -1) :
	fkai[i-1] = fkai[i] * i
	fkai[i-1] %= md
def comb(n, r) :
	if r < 0 or n < r :
		return 0
	return (kai[n] * fkai[r] * fkai[n - r]) % md

cnt = [0] * (N + 1)
for a in A :
	if a > 0 :
		cnt[a] += 1
res = []
for i in range(1, N+1) :
	if cnt[i] == 0 :
		res.append(i)
res.append(N+100)
siz = len(res) - 1
ans = 0
mi = 0
fl = 0
m1 = 0
for a in A :
	mi = max(mi, a)
	while (res[fl] < mi) :
		fl += 1
	if a == mi :
		p = comb(fl, m1)
		p *= kai[m1]
		p %= md
		p *= kai[siz - m1]
		p %= md
		ans += p
	if a == -1 :
		p = md + comb(siz, m1+1) - comb(fl, m1+1)
		p *= kai[m1]
		p %= md
		p *= kai[siz - m1 - 1]
		p %= md
		ans += p
		m1 += 1
	ans %= md
print(ans)