func_code_string: #include <bits/stdc++.h>   using namespace std;   constexpr int N = 2e5 + 3;   vector<int> c[N];   vector<int> e[N];   int main() {     ios_base::sync_with_stdio(false);     int n, m, q;     cin >> n >> m >> q;     for (int it = 0; it < q; ++it) {       int r, C;       cin >> r >> C;       c[r].push_back(C);     }     for (int i = 1; i <= n; ++i) {       int esz = c[i].size();       for (int j = 1; j < esz; ++j) {         int prev = c[i][j - 1], now = c[i][j];         e[prev].push_back(now);         e[now].push_back(prev);       }     }     vector<int> vis(m + 1, 0);     int cc = 0;     for (int i = 1; i <= m; ++i) {       if (vis[i] == 0) {         ++cc;         function<void(int)> dfs = [&](int i) {           assert(i >= 1 && i <= m);           if (vis[i] != 0) {             assert(vis[i] == cc);             return;           }           vis[i] = cc;           for (int v : e[i]) {             dfs(v);           }         };         dfs(i);       }     }     int cnt_empty_r = 0;     for (int i = 1; i <= n; ++i) {       if (c[i].empty()) {         ++cnt_empty_r;       }     }     cout << cnt_empty_r + cc - 1 <<   n ;   }   