func_code_string: #include <bits/stdc++.h>   using namespace std;   using ll = long long;   template <class t, class u>   void chmax(t& first, u second) {     if (first < second) first = second;   }   template <class t, class u>   void chmin(t& first, u second) {     if (second < first) first = second;   }   template <class t>   using vc = vector<t>;   template <class t>   using vvc = vc<vc<t>>;   using pi = pair<ll, ll>;   using vi = vc<ll>;   template <class t, class u>   ostream& operator<<(ostream& os, const pair<t, u>& p) {     return os <<  {  << p.first <<  ,  << p.second <<  } ;   }   template <class t>   ostream& operator<<(ostream& os, const vc<t>& v) {     os <<  { ;     for (auto e : v) os << e <<  , ;     return os <<  } ;   }   using uint = unsigned;   using ull = unsigned long long;   template <class t, size_t n>   ostream& operator<<(ostream& os, const array<t, n>& first) {     return os << vc<t>(first.begin(), first.end());   }   template <ll i, class T>   void print_tuple(ostream&, const T&) {}   template <ll i, class T, class H, class... Args>   void print_tuple(ostream& os, const T& t) {     if (i) os <<  , ;     os << get<i>(t);     print_tuple<i + 1, T, Args...>(os, t);   }   template <class... Args>   ostream& operator<<(ostream& os, const tuple<Args...>& t) {     os <<  { ;     print_tuple<0, tuple<Args...>, Args...>(os, t);     return os <<  } ;   }   template <class t>   void print(t x, ll suc = 1) {     cout << x;     if (suc == 1) cout <<   n ;     if (suc == 2) cout <<    ;   }   ll read() {     ll i;     cin >> i;     return i;   }   vi readvi(ll n, ll off = 0) {     vi v(n);     for (ll i = ll(0); i < ll(n); i++) v[i] = read() + off;     return v;   }   pi readpi(ll off = 0) {     ll first, second;     cin >> first >> second;     return pi(first + off, second + off);   }   template <class T>   void print(const vector<T>& v, ll suc = 1) {     for (ll i = ll(0); i < ll(v.size()); i++)       print(v[i], i == ll(v.size()) - 1 ? suc : 2);   }   string readString() {     string s;     cin >> s;     return s;   }   template <class T>   T sq(const T& t) {     return t * t;   }   void yes(bool ex = true) {     cout <<  Yes           <<   n ;     if (ex) exit(0);   }   void no(bool ex = true) {     cout <<  No           <<   n ;     if (ex) exit(0);   }   void possible(bool ex = true) {     cout <<  Possible           <<   n ;     if (ex) exit(0);   }   void impossible(bool ex = true) {     cout <<  Impossible           <<   n ;     if (ex) exit(0);   }   constexpr ll ten(ll n) { return n == 0 ? 1 : ten(n - 1) * 10; }   const ll infLL = LLONG_MAX / 3;   const ll inf = infLL;   ll topbit(signed t) { return t == 0 ? -1 : 31 - __builtin_clz(t); }   ll topbit(ll t) { return t == 0 ? -1 : 63 - __builtin_clzll(t); }   ll botbit(signed first) { return first == 0 ? 32 : __builtin_ctz(first); }   ll botbit(ll first) { return first == 0 ? 64 : __builtin_ctzll(first); }   ll popcount(signed t) { return __builtin_popcount(t); }   ll popcount(ll t) { return __builtin_popcountll(t); }   bool ispow2(ll i) { return i && (i & -i) == i; }   ll mask(ll i) { return (ll(1) << i) - 1; }   bool inc(ll first, ll second, ll c) { return first <= second && second <= c; }   template <class t>   void mkuni(vc<t>& v) {     sort(v.begin(), v.end());     v.erase(unique(v.begin(), v.end()), v.end());   }   ll rand_int(ll l, ll r) {     static mt19937_64 gen(chrono::steady_clock::now().time_since_epoch().count());     return uniform_int_distribution<ll>(l, r)(gen);   }   template <class t>   void myshuffle(vc<t>& first) {     for (ll i = ll(0); i < ll(ll(first.size())); i++)       swap(first[i], first[rand_int(0, i)]);   }   template <class t>   ll lwb(const vc<t>& v, const t& first) {     return lower_bound(v.begin(), v.end(), first) - v.begin();   }   signed main() {     cin.tie(0);     ios::sync_with_stdio(0);     cout << fixed << setprecision(20);     ll n;     cin >> n;     ll k = n / 2;     vi x(k), y(n - k);     for (ll i = ll(0); i < ll(k); i++) x[i] = i + 1;     for (ll i = ll(0); i < ll(n - k); i++) y[i] = k + i + 1;     vvc<ll> ans;     if (n % 2) {       for (ll i = ll(0); i < ll(k); i++)         for (ll j = ll(i + 1); j < ll(k); j++)           for (ll _ = ll(0); _ < ll(2); _++) {             ans.push_back({x[i], x[j], y[i], y[j]});           }       for (ll i = ll(0); i < ll(k); i++)         for (ll _ = ll(0); _ < ll(2); _++) ans.push_back({x[i], y[k], y[i]});     } else {       for (ll i = ll(0); i < ll(k); i++) {         for (ll j = ll(i + 2); j < ll(i == 0 ? k - 1 : k); j++)           for (ll _ = ll(0); _ < ll(2); _++) {             ans.push_back({x[i], x[j], y[i], y[j]});           }         if (k >= 3) {           if (i + 1 < k) {             ll j = i + 1;             ans.push_back({x[i], x[j], y[i], y[j]});           }           if (i == 0) {             ll j = k - 1;             ans.push_back({x[i], x[j], y[i], y[j]});           }         }         {           ans.push_back({x[i], x[(i + 1) % k], y[(i + 1) % k]});           ans.push_back({x[(i + 1) % k], y[i], y[(i + 1) % k]});         }       }     }     print(ll(ans.size()));     for (auto vs : ans) {       print(ll(vs.size()), 2);       print(vs);     }     vvc<ll> cnt(n, vi(n));     for (auto vs : ans) {       for (ll i = ll(0); i < ll(ll(vs.size())); i++) {         ll p = vs[i] - 1, q = vs[(i + 1) % ll(vs.size())] - 1;         cnt[p][q]++;         cnt[q][p]++;       }     }     void(0);     for (ll i = ll(0); i < ll(n); i++)       for (ll j = ll(0); j < ll(n); j++)         if (i != j) {           assert(cnt[i][j] == 2);         }   }   