func_code_string: #include <bits/stdc++.h>   using namespace std;   const int maxn = 1e5 + 5;   const int maxm = 1e5 + 5;   const long double eps = 1e-14;   const long double eps2 = 1e-9;   const long double INF = 1 << 30;   inline int dcmp(const long double& x) {     return fabs(x) < eps ? 0 : (x < 0 ? -1 : 1);   }   pair<long double, long double> operator+(       const pair<long double, long double>& a,       const pair<long double, long double>& b) {     return {a.first + b.first, a.second + b.second};   }   pair<long double, long double> operator-(       const pair<long double, long double>& a,       const pair<long double, long double>& b) {     return {a.first - b.first, a.second - b.second};   }   pair<long double, long double> operator*(       const pair<long double, long double>& a, const long double& b) {     return {a.first * b, a.second * b};   }   long double dot(const pair<long double, long double>& a,                   const pair<long double, long double>& b) {     return a.first * b.first + a.second * b.second;   }   long double cross(const pair<long double, long double>& a,                     const pair<long double, long double>& b) {     return a.first * b.second - a.second * b.first;   }   long double abs(const pair<long double, long double>& a) {     return sqrt(dot(a, a));   }   long double interPnt(pair<long double, long double> p1,                        pair<long double, long double> p2,                        pair<long double, long double> q1,                        pair<long double, long double> q2) {     pair<long double, long double> d = p2 - p1, e = q2 - q1;     long double crs = cross(d, e);     if (abs(crs) < eps) {       long double c2 = cross(d, q1 - p1);       if (abs(c2) > eps) return INF;       long double da2 = dot(d, d);       long double f1 = dot(d, q1 - p1) / da2;       long double f2 = dot(d, q2 - p1) / da2;       if (f1 < -eps and f2 < -eps) return INF;       if (f1 > 1 + eps and f2 > 1 + eps) return INF;       long double f = max(0.l, min(f1, f2));       return (p1 + d * f).first;     }     assert(0);   }   template <typename T>   inline bool getmin(T& a, const T& b) {     return dcmp(b - a) < 0 ? (a = b, true) : false;   }   template <typename T>   inline bool getmax(T& a, const T& b) {     return dcmp(b - a) > 0 ? (a = b, true) : false;   }   struct Iron {     int show, speed, st, ed;     inline void read() {       scanf( %d%d%d%d , &show, &speed, &st, &ed);       st--, ed--;     }   } iron[maxm];   struct Iron2 {     long double from, fromt, to, tot;   };   struct Path {     int id, from, to;   };   struct Event {     long double t;     int segid;     bool operator<(const Event& rhs) const { return dcmp(t - rhs.t) < 0; }   };   int n, m;   vector<int> G[maxn], chain[maxn];   int fa[maxn], dep[maxn], chainid[maxn], size[maxn];   int pre[maxn], dfs_clock;   void dfs(int now) {     vector<int>& vec = chain[chainid[now]];     for (int i = ((int)(vec.size())) - 1; i >= 0; i--) pre[vec[i]] = dfs_clock++;     for (int i = 0; i < ((int)(vec.size())); i++) {       int now = vec[i];       for (const int& to : G[now])         if ((!i || to != vec[i - 1]) && to != fa[now]) dfs(to);     }   }   inline void make_HLD() {     int first = 0, last = 0;     int* q = new int[n];     q[last++] = 0;     fa[0] = -1;     dep[0] = 0;     while (last - first > 0) {       int now = q[first++];       for (const int& to : G[now])         if (to != fa[now]) {           fa[to] = now;           dep[to] = dep[now] + 1;           q[last++] = to;         }     }     for (int i = last - 1; i >= 0; i--) {       int now = q[i], hs = -1;       size[now] = 1;       for (const int& to : G[now])         if (to != fa[now]) {           size[now] += size[to];           if (hs < 0 || size[to] > size[hs]) hs = to;         }       if (hs < 0)         chainid[now] = now;       else         chainid[now] = chainid[hs];       chain[chainid[now]].push_back(now);     }     dfs_clock = 0;     delete[] q;     dfs(0);   }   inline bool inrange(const long double& x, const long double& L,                       const long double& R) {     return dcmp(x - L) >= 0 && dcmp(x - R) <= 0;   }   inline long double getIntersectime(const Iron2& A, const Iron2& B) {     const long double &x1 = A.from, &t1 = A.fromt, &x2 = A.to, &t2 = A.tot,                       &x3 = B.from, &t3 = B.fromt, &x4 = B.to, &t4 = B.tot;     long double deno = (x2 - x1) * (t4 - t3) - (t2 - t1) * (x4 - x3);     long double nume = (x3 - x1) * (t2 - t1) * (t4 - t3) -                        t3 * (t2 - t1) * (x4 - x3) + t1 * (t4 - t3) * (x2 - x1);     long double ans;     if (dcmp(deno) == 0) {       return interPnt(make_pair(t1, x1), make_pair(t2, x2), make_pair(t3, x3),                       make_pair(t4, x4));       if (dcmp((x4 - x3) / (t4 - t3) * (t1 - t3) + x3 - x1) == 0)         ans = max(t1, t3);       else         ans = INF;     } else       ans = nume / deno;     if (inrange(ans, max(t1, t3), min(t2, t4)))       return ans;     else       return INF;   }   long double curtime;   vector<Iron2> vec;   struct cmp {     inline long double getpos(const Iron2& I, const long double& t) const {       return I.from + ((I.to - I.from) / (I.tot - I.fromt)) * (t - I.fromt);     }     bool operator()(const int& a, const int& b) const {       long double d1 = dcmp(getpos(vec[a], curtime) - getpos(vec[b], curtime)),                   d2 = dcmp(getpos(vec[a], curtime + 1) -                             getpos(vec[b], curtime + 1));       return d1 < 0 || (d1 == 0 && d2 < 0) || (d1 == 0 && d2 == 0 && a < b);     }   };   vector<Iron2> Seg[maxn];   inline long double solve_path(const int& nowSeg) {     vec = Seg[nowSeg];     set<int, cmp> second;     vector<Event> eve;     for (int i = 0; i < ((int)(vec.size())); i++)       eve.push_back((Event){vec[i].fromt, i << 1}),           eve.push_back((Event){vec[i].tot, i << 1 | 1});     sort(eve.begin(), eve.end());     long double ans = INF;     for (const Event& e : eve) {       curtime = e.t;       if (dcmp(curtime - ans) >= 0) break;       int id = e.segid;       if (!(id & 1)) {         id /= 2;         set<int>::iterator it = second.lower_bound(id);         assert(second.find(id) == second.end());         if (it != second.end()) getmin(ans, getIntersectime(vec[id], vec[*it]));         if (it != second.begin())           it--, getmin(ans, getIntersectime(vec[id], vec[*it]));         second.insert(id);       } else {         id /= 2;         set<int>::iterator it = second.lower_bound(id), itL = it, itR = it;         assert((*it) == id);         itR++;         if (itL != second.begin() && itR != second.end()) {           itL--;           getmin(ans, getIntersectime(vec[*itL], vec[*itR]));         }         second.erase(it);       }     }     return ans;   }   vector<Path> path, L, R;   inline void getPath(int a, int b) {     L.clear();     R.clear();     while (chainid[a] != chainid[b]) {       int atop = chain[chainid[a]].back(), btop = chain[chainid[b]].back();       if (dep[atop] > dep[btop])         L.push_back((Path){chainid[a], a, fa[atop]}), a = fa[atop];       else         R.push_back((Path){chainid[b], fa[btop], b}), b = fa[btop];     }     L.push_back((Path){chainid[a], a, b});     path.clear();     for (int i = 0; i < ((int)(L.size())); i++) path.push_back(L[i]);     for (int i = ((int)(R.size())) - 1; i >= 0; i--) path.push_back(R[i]);   }   inline int PosOnPath(int id, int now) {     if (chainid[now] != id) return 0;     return pre[now] - pre[chain[id].back()] + 1;   }   inline long double solve_tree() {     make_HLD();     for (int i = 0; i < m; i++) {       getPath(iron[i].st, iron[i].ed);       long double curt = iron[i].show, v = iron[i].speed;       for (const Path& p : path) {         int from = PosOnPath(p.id, p.from), to = PosOnPath(p.id, p.to);         long double arrt = curt + abs(to - from) / v;         long double cc = dcmp(arrt - curt) == 0 ? 0 : (to - from) / (arrt - curt);         Seg[p.id].push_back(             (Iron2){from - eps2 * cc, curt - eps2, to + eps2 * cc, arrt + eps2});         curt = arrt;       }     }     long double res = INF;     for (int i = 0; i < n; i++) getmin(res, solve_path(i));     return res;   }   int main() {     scanf( %d%d , &n, &m);     for (int i = 0, a, b; i < n - 1; i++) {       scanf( %d%d , &a, &b);       a--, b--;       G[a].push_back(b);       G[b].push_back(a);     }     for (int i = 0; i < m; i++) iron[i].read();     long double ans = solve_tree();     if (dcmp(ans - INF) >= 0)       printf( -1 n );     else       printf( %.13f n , (double)ans);   }   