#include<bits/stdc++.h>
using namespace std;
using ll=long long;
constexpr int MOD=998244353;
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define rep2(i,l,r) for(int i=(l);i<(int)(r);i++)
#define all(v) v.begin(),v.end()

namespace Lib{
  struct mod_fac{
    vector <ll> fac,inv,invf;
    mod_fac (int n):
      fac(n),inv(n),invf(n){
      fac[0]=fac[1]=1;
      inv[0]=inv[1]=1;
      invf[0]=invf[1]=1;
      for(int i=2;i<n;i++){
        fac[i]=fac[i-1]*i%MOD;
        inv[i]=inv[MOD%i]*(MOD-MOD/i)%MOD;
        invf[i]=invf[i-1]*inv[i]%MOD;
      }
    }
    ll comb(int n,int r){
      return fac[n]*invf[r]%MOD*invf[n-r]%MOD;
    }
    ll perm(int n,int r){
      return fac[n]*invf[n-r]%MOD;
    }
  };
}

void ch(ll &a,ll b){
  a=(a+b)%MOD;
}
int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int N;
  cin>>N;
  vector A(N,0);
  for(auto &i:A)cin>>i,--i;
  vector used(N,0);
  for(int i:A){
    if(i!=-2)used[i]=1;
  }
  vector unused(0,0);
  rep(i,N){
    if(!used[i])unused.push_back(i);
  }
  int max_p=-1,free_p=0;
  ll ans=0;
  Lib::mod_fac F(N*2);
  for(auto i:A){
    if(i==-2){
      int idx=lower_bound(all(unused),max_p)-unused.begin();
      ll t=F.comb(unused.size(),free_p+1)*F.fac[free_p]%MOD;
      if(idx>=free_p+1){
        ch(t,-(F.comb(idx,free_p+1)*F.fac[free_p]));
      }
      ch(ans,t*F.fac[(int)unused.size()-free_p-1]);
      free_p+=1;
    }else{
      int idx=lower_bound(all(unused),i)-unused.begin();
      if(idx>=free_p&&i>max_p){
        ch(ans,F.perm(idx,free_p)*F.fac[(int)unused.size()-free_p]);
      }
      max_p=max(max_p,i);
    }
  }
  if(ans<0)ans+=MOD;
  cout<<ans<<'\n';
}