#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

class Comb
{
  int siz, mod;
  std::vector<long long> _fac, _inv, _finv;
public:
  // 引数は (mod)
  Comb(int m) : mod(m), siz(2)
  {
    _fac.resize(siz);
    _inv.resize(siz);
    _finv.resize(siz);
    _fac[0] = _fac[1] = _inv[1] = _finv[0] = _finv[1] = 1;
  }
  long long p(int n, int k)
  {
    if (n < k || k < 0) return 0;
    resize(n + 1);
    return _fac[n] * _finv[n - k] % mod;
  }
  long long c(int n, int k)
  {
    if (n < k || k < 0) return 0;
    resize(n + 1);
    return _fac[n] * _finv[k] % mod * _finv[n - k] % mod;
  }
  long long inv(int n)
  {
    resize(n + 1);
    if (n < 0) return 0;
    else return _inv[n];
  }
  long long fac(int n)
  {
    resize(n + 1);
    if (n < 0) return 0;
    else return _fac[n];
  }
  long long finv(int n)
  {
    resize(n + 1);
    if (n < 0) return 0;
    else return _finv[n];
  }
private:
  void resize(int n)
  {
    if (n <= siz) return;
    for (int i = siz; i < n; ++i)
    {
      _fac.push_back((long long)i * _fac[i - 1] % mod);
      _inv.push_back(mod - _inv[mod % i] * (mod / i) % mod);
      _finv.push_back(_finv[i - 1] * _inv[i] % mod);
    }
    siz = n;
  }
};

int main()
{
  const int mod = 998244353;
  int n;
  cin >> n;
  vector<int> a(n), flag(n);
  for (int i = 0; i < n; ++i) cin >> a[i];
  for (int i = 0; i < n; ++i) a[i] = max(-1, a[i] - 1);
  for (int i = 0; i < n; ++i) if (a[i] != -1) flag[a[i]] = 1;
  vector<int> val;
  for (int i = 0; i < n; ++i) if (!flag[i]) val.push_back(i);
  Comb cb(mod);
  long long ans = 0;
  int cnt = 0, ma = 0, siz = val.size();
  for (int i = 0; i < n; ++i)
  {
    if (a[i] != -1)
    {
      if (ma > a[i]) continue;
      int tmp = lower_bound(val.begin(), val.end(), a[i]) - val.begin();
      ans = (ans + cb.p(tmp, cnt) * cb.fac(siz - cnt)) % mod;
      ma = a[i];
    }
    else
    {
      int tmp = lower_bound(val.begin(), val.end(), ma) - val.begin();
      ans = (ans + (cb.c(siz, cnt + 1) - cb.c(tmp, cnt + 1) + mod) * cb.fac(cnt) % mod * cb.fac(siz - cnt - 1)) % mod;
      ++cnt;
    }
  }
  cout << ans << endl;
}