func_code_string: #include <bits/stdc++.h>   using namespace std;   map<pair<int, int>, int> ord;   vector<pair<int, int> > edges;   vector<int> adj[200000];   int n;   int main() {     cin >> n;     cout << n - 1 << endl;     for (int i = 1; i < n; i++) {       int a, b;       cin >> a >> b;       edges.push_back(make_pair(a, b));       ord[make_pair(a, b)] = ord[make_pair(b, a)] = i;       adj[a].push_back(b);       adj[b].push_back(a);       cout <<  2   << a <<     << b << endl;     }     for (int i = 1; i <= n; i++)       for (int j = 0; j < adj[i].size() - 1; j++)         cout << ord[make_pair(i, adj[i][j])] <<                  << ord[make_pair(i, adj[i][j + 1])] << endl;   }   