func_code_string: #include <bits/stdc++.h>   using namespace std;   const int dy[] = {-1, 0, 1, 0}, dx[] = {0, 1, 0, -1};   const double EPS = 1e-8;   const double PI = acos(-1.0);   int popcount(int n) { return __builtin_popcount(n); }   int popcount(long long n) { return __builtin_popcountll(n); }   template <class T>   int SIZE(T a) {     return a.size();   }   template <class T>   string IntToString(T num) {     string res;     stringstream ss;     ss << num;     return ss.str();   }   template <class T>   T StringToInt(string str) {     T res = 0;     for (int i = 0; i < SIZE(str); i++) res = (res * 10 + str[i] -  0 );     return res;   }   template <class T>   T gcd(T a, T b) {     if (b == 0) return a;     return gcd(b, a % b);   }   template <class T>   T lcm(T a, T b) {     return a / gcd(a, b) * b;   }   template <class T>   void PrintSeq(T &a, int sz) {     for (int i = 0; i < sz; i++) {       cout << a[i];       if (sz == i + 1)         cout << endl;       else         cout <<    ;     }   }   bool EQ(double a, double b) { return abs(a - b) < EPS; }   void fastStream() {     cin.tie(0);     std::ios_base::sync_with_stdio(0);   }   vector<string> split(string str, char del) {     vector<string> res;     for (int i = 0, s = 0; i < SIZE(str); i++) {       if (str[i] == del) {         if (i - s != 0) res.push_back(str.substr(s, i - s));         s = i + 1;       } else if (i == SIZE(str) - 1) {         res.push_back(str.substr(s));       }     }     return res;   }   int froms[1000001];   int tos[1000001];   vector<pair<int, int> > G[1000001];   bool used[1000001];   void dfs(int pprv, int prv, int now) {     used[now] = true;     for (int i = 0; i < (int)G[now].size(); i++) {       int to = G[now][i].first;       int en = G[now][i].second;       if (!used[to]) {         dfs(prv, en, to);       }     }     if (prv != -1 && pprv != -1) cout << pprv <<     << prv << endl;   }   int main() {     fastStream();     int N;     cin >> N;     for (int i = 0; i < N - 1; i++) {       cin >> froms[i] >> tos[i];       G[froms[i]].push_back(make_pair(tos[i], i + 1));       G[tos[i]].push_back(make_pair(froms[i], i + 1));     }     cout << N - 1 << endl;     for (int i = 0; i < N - 1; i++)       cout << 2 <<     << froms[i] <<     << tos[i] << endl;     for (int i = 0; i < N; i++) {       if (G[i + 1].size() == 1) {         dfs(-1, -1, i + 1);         break;       }     }     return 0;   }   