#include <bits/stdc++.h>
#include <atcoder/all>

using namespace std;
using namespace atcoder;

struct Fast {
  Fast() {
    std::cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << setprecision(10);
  }
} fast;

#define all(a) (a).begin(), (a).end()
#define contains(a, x) ((a).find(x) != (a).end())
#define rep(i, a, b) for (int i = (a); i < (int)(b); i++)
#define rrep(i, a, b) for (int i = (int)(b)-1; i >= (a); i--)
#define writejoin(s, a) rep(_i, 0, (a).size()) cout << (a)[_i] << (_i + 1 < (int)(a).size() ? s : "\n");
#define YN(b) cout << ((b) ? "YES" : "NO") << "\n";
#define Yn(b) cout << ((b) ? "Yes" : "No") << "\n";
#define yn(b) cout << ((b) ? "yes" : "no") << "\n";

using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vl = vector<ll>;
using mint = modint998244353;
using vm = vector<mint>;

void solve() {
  int n;
  cin >> n;
  vi c(n, 0);
  rep(i, 0, n) {
    int a;
    cin >> a;
    if (a < n) c[a]++;
  }
  vector<modint1000000007> dp(n + 1, 0);
  dp[0] = 1;
  rep(i, 0, n) rrep(j, 0, i + 1) dp[j + 1] += dp[j] * c[i];
  modint1000000007 ans = 0, f = 1;
  for (int i = n; i >= 0; i--, f *= n - i)
    ans += (1 - (i & 1) * 2) * dp[i] * f;
  cout << ans.val() << endl;
}

int main() {
  int t = 1;
  // cin >> t;
  while (t--) solve();
}