func_code_string: #include <bits/stdc++.h>   using namespace std;   const long long M = 998244353;   long long f[300005];   vector<long long> m1[300005], m2[300005];   int32_t main() {     std::ios::sync_with_stdio(0);     std::cin.tie(0);     ;     long long n;     cin >> n;     for (long long i = 0; i < n; i++) {       long long x, y;       cin >> x >> y;       m1[x].push_back(y);       m2[y].push_back(x);     }     f[0] = 1;     for (long long i = 1; i < 300005; i++) f[i] = f[i - 1] * i % M;     long long ans = f[n], d1 = 1, d2 = 1, d3 = 1;     for (long long i = 1; i <= n; i++) d1 = d1 * f[m1[i].size()] % M;     for (long long i = 1; i <= n; i++) d2 = d2 * f[m2[i].size()] % M;     ans = ((ans - d1 - d2) % M + M) % M;     vector<long long> a, b;     for (long long i = 1; i <= n; i++) {       if (m1[i].size() == 0) continue;       sort((m1[i]).begin(), (m1[i]).end());       map<long long, long long> m;       for (long long e : m1[i]) m[e]++;       for (pair<long long, long long> p : m) d3 = d3 * f[p.second] % M;       a.push_back(i);       b.push_back(m1[i][0]);       b.push_back(m1[i].back());     }     for (long long i = 0; i < a.size() - 1; i++)       if (a[i + 1] < a[i]) d3 = 0;     for (long long i = 0; i < b.size() - 1; i++)       if (b[i + 1] < b[i]) d3 = 0;     ans = (ans + d3) % M;     cout << ans <<   n ;   }   