import sys

sys.setrecursionlimit(200005)
# sys.set_int_max_str_digits(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
# inf = -1-(-1 << 31)
inf = -1-(-1 << 62)

# md = 10**9+7
md = 998244353

def nCr(com_n, com_r):
    if com_r < 0: return 0
    if com_n < com_r: return 0
    return fac[com_n]*ifac[com_r]%md*ifac[com_n-com_r]%md

def nPr(com_n, com_r):
    if com_r < 0: return 0
    if com_n < com_r: return 0
    return fac[com_n]*ifac[com_n-com_r]%md

n_max = 200005
fac = [1]
for i in range(1, n_max+1): fac.append(fac[-1]*i%md)
ifac = [1]*(n_max+1)
ifac[n_max] = pow(fac[n_max], md-2, md)
for i in range(n_max-1, 1, -1): ifac[i] = ifac[i+1]*(i+1)%md

n=II()
aa=LI1()
cs=[1]*n
for a in aa:
    if a==-2:continue
    cs[a]=0
for i in range(n-1):cs[i+1]+=cs[i]

mx=-inf
tot=aa.count(-2)
cnt=0
ans=0
for a in aa:
    if a==-2:
        cnt+=1
        if mx==-inf:
            ans+=nCr(tot,cnt)*fac[cnt-1]%md*fac[tot-cnt]%md
        else:
            ans+=(nCr(tot,cnt)-nCr(cs[mx],cnt))*fac[cnt-1]%md*fac[tot-cnt]%md
        ans%=md
    elif a>mx:
        ans+=nPr(cs[a],cnt)*fac[tot-cnt]%md
        ans%=md
        mx=a
print(ans)