func_code_string: #include <bits/stdc++.h>   using namespace std;   int n, m;   vector<int> ke[1000010];   bool cx[1000010], visited[1000010];   void dfs(int u) {     visited[u] = true;     for (int v : ke[u])       if (!visited[v]) dfs(v);   }   long long c2(int x) { return (1LL * x * (x - 1)) >> 1; }   int main() {     if (fopen( a.txt ,  r )) {       freopen( a.txt ,  r , stdin);     } else       ios_base::sync_with_stdio(false);     cin.tie(NULL);     cin >> n >> m;     int own = 0;     for (int i = 1; i <= m; i++) {       int u, v;       cin >> u >> v;       cx[u] = true;       cx[v] = true;       if (u != v) {         ke[u].push_back(v);         ke[v].push_back(u);       } else         own++;     }     int cnt = 0;     for (int u = 1; u <= n; u++)       if (cx[u] && !visited[u]) {         dfs(u);         cnt++;       }     if (cnt != 1) {       cout << 0;       exit(0);     };     long long res = 0;     for (int i = 1; i <= n; i++) res += c2(int(ke[i].size()));     res += c2(own);     res += 1LL * own * (m - own);     cout << res;   }   