#include <bits/stdc++.h>
using namespace std;
long long power(long long x, long long y, long long md = 998244353) {
  long long res = 1;
  x %= md;
  while (y > 0) {
    if (y & 1) res = (res * x) % md;
    x = (x * x) % md;
    y = y >> 1;
  }
  return res % md;
}
long long min1() { return 1000000000000000LL; }
long long max1() { return -1000000000000000LL; }
template <typename... Args>
long long min1(long long a, Args... args) {
  return min(a, min1(args...));
}
template <typename... Args>
long long max1(long long a, Args... args) {
  return max(a, max1(args...));
}
struct node {
  std::vector<long long> v, w;
};
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  long long n;
  cin >> n;
  vector<pair<long long, long long> > second(n);
  for (long long i = 0; i < n; i++) cin >> second[i].first >> second[i].second;
  long long first[300002];
  first[0] = 1;
  for (long long i = 1; i < 300002; i++)
    first[i] = (first[i - 1] * i) % 998244353;
  map<long long, map<long long, long long> > make_pair;
  for (long long i = 0; i < n; i++) {
    make_pair[second[i].first][second[i].second]++;
  }
  long long tot = 1;
  long long mn = 1;
  long long prev = -1000000000000000LL;
  for (map<long long, map<long long, long long> >::iterator it =
           make_pair.begin();
       it != make_pair.end(); ++it) {
    long long temp = 1;
    long long t1 = 0;
    for (map<long long, long long>::iterator it1 = (it->second).begin();
         it1 != (it->second).end(); it1++) {
      temp *= first[it1->second];
      t1 += it1->second;
      t1 %= 998244353;
      temp %= 998244353;
    }
    t1 = first[t1];
    map<long long, long long>::iterator it2 = (it->second).begin();
    if (it2->first >= prev)
      mn *= temp;
    else
      mn = 0;
    it2 = std::prev((it->second).end());
    prev = it2->first;
    mn %= 998244353;
    tot *= t1;
    tot %= 998244353;
  }
  make_pair.clear();
  long long tot1 = 1;
  for (long long i = 0; i < n; i++) {
    make_pair[second[i].second][second[i].first]++;
  }
  for (map<long long, map<long long, long long> >::iterator it =
           make_pair.begin();
       it != make_pair.end(); ++it) {
    long long temp = 1;
    long long t1 = 0;
    for (map<long long, long long>::iterator it1 = (it->second).begin();
         it1 != (it->second).end(); it1++) {
      temp *= first[it1->second];
      t1 += it1->second;
      t1 %= 998244353;
      temp %= 998244353;
    }
    t1 = first[t1];
    tot1 *= t1;
    tot1 %= 998244353;
  }
  long long ans = first[n];
  ans -= tot + tot1 - mn;
  ans %= 998244353;
  ans += 998244353;
  ans %= 998244353;
  cout << ans << '\n';
}
