func_code_string: #include <bits/stdc++.h>   using namespace std;   const int mxN = 200000;   int n, m, t, tin[mxN];   vector<int> adj[mxN], e[mxN];   vector<array<int, 3>> ans;   void dfs(int u, int p = -1) {     tin[u] = ++t;     if (p ^ -1) e[u].push_back(p);     for (int v : adj[u]) {       if (v == p) continue;       if (!tin[v]) {         dfs(v, u);       } else if (tin[v] < tin[u]) {         e[u].push_back(v);       }     }     while (e[u].size() >= 2) {       int v = e[u].back();       e[u].pop_back();       int w = e[u].back();       e[u].pop_back();       ans.push_back({v, u, w});     }     if (e[u].size() == 1 && p ^ -1) e[p].push_back(u);   }   int main() {     ios::sync_with_stdio(0);     cin.tie(0);     cin >> n >> m;     for (int i = 0; i < m; ++i) {       int u, v;       cin >> u >> v, --u, --v;       adj[u].push_back(v);       adj[v].push_back(u);     }     for (int i = 0; i < n; ++i)       if (!tin[i]) dfs(i);     cout << ans.size() <<   n ;     for (array<int, 3> x : ans)       cout << x[0] + 1 <<     << x[1] + 1 <<     << x[2] + 1 <<   n ;     return 0;   }   