func_code_string: #include <bits/stdc++.h>   using namespace std;   template <class T>   inline void read(T &x) {     x = 0;     char c = getchar();     int f = 1;     while (!isdigit(c)) {       if (c ==  - ) f = -1;       c = getchar();     }     while (isdigit(c)) {       x = x * 10 + c -  0 ;       c = getchar();     }     x *= f;   }   template <class T>   inline void umin(T &x, T y) {     x = x < y ? x : y;   }   template <class T>   inline void umax(T &x, T y) {     x = x > y ? x : y;   }   inline unsigned int R() {     static unsigned int seed = 416;     return seed ^= seed >> 5, seed ^= seed << 17, seed ^= seed >> 13;   }   const int N = 266666;   const double inf = 1e9, eps = 1e-6;   int n, m, fa[N], top[N], dep[N], sz[N], son[N], dfn[N], idfn[N], num;   vector<int> e[N];   double ans = inf, cur;   struct dot {     double x, y;     dot(double X = 0, double Y = 0) {       x = X;       y = Y;     }   };   vector<pair<dot, dot> > mrk[N];   dot a[N], b[N];   int len;   pair<double, int> ev[N];   bool cmp1(pair<double, int> a, pair<double, int> b) {     return a.first != b.first ? a.first < b.first : a.second > b.second;   }   inline double gety(int i) {     return a[i].x == b[i].x                ? a[i].y                : a[i].y + (cur - a[i].x) / (b[i].x - a[i].x) * (b[i].y - a[i].y);   }   struct node {     int u;     bool operator<(const node &a) const {       return gety(u) != gety(a.u) ? gety(u) < gety(a.u) : u < a.u;     }   };   set<node> Set;   dot operator-(dot a, dot b) { return dot(a.x - b.x, a.y - b.y); }   double Cross(dot a, dot b) { return a.x * b.y - a.y * b.x; }   bool isin(dot p, dot a, dot b) {     return p.x >= min(a.x, b.x) - eps && p.x <= max(a.x, b.x) + eps &&            p.y >= min(a.y, b.y) - eps && p.y <= max(a.y, b.y) + eps;   }   double Abs(double x) { return x > 0 ? x : -x; }   bool on_line(dot p, dot a, dot b) { return Abs(Cross(p - a, b - a)) <= eps; }   double getlen(dot a) { return sqrt(a.x * a.x + a.y * a.y); }   void print(int i) {     printf( %lf %lf %lf %lf n , a[i].x, a[i].y, b[i].x, b[i].y);   }   double getans(int i, int j) {     if (i == j) return inf;     if (getlen(b[i] - a[i]) > getlen(b[j] - a[j])) swap(i, j);     if (getlen(b[i] - a[i]) <= eps) {       if (isin(a[i], a[j], b[j]) && on_line(a[i], a[j], b[j])) return a[i].x;       return inf;     }     dot A = a[i], B = b[i], C = a[j], D = b[j], u = B - A, v = D - C;     if (Abs(Cross(u, v)) <= eps) {       if (Abs(gety(i) - gety(j)) <= eps && cur >= A.x - eps && cur <= B.x + eps &&           cur >= C.x - eps && cur <= D.x + eps) {         return cur;       }       return inf;     }     double k = (Cross(D, v) - Cross(A, v)) / Cross(u, v);     dot p(A.x + k * u.x, A.y + k * u.y);     if (isin(p, A, B) && isin(p, C, D) && on_line(p, A, B) && on_line(p, C, D))       return A.x + k * u.x;     return inf;   }   void upd(int i) {     set<node>::iterator it = Set.lower_bound((node){i});     if (it != Set.end()) umin(ans, getans(i, (*it).u));     if (it != Set.begin()) it--, umin(ans, getans(i, (*it).u));   }   void dfs1(int u, int Fa, int Dep) {     fa[u] = Fa;     dep[u] = Dep;     sz[u] = 1;     for (register int i = (0); i <= (((int)e[u].size()) - 1); i++)       if (e[u][i] != Fa) {         dfs1(e[u][i], u, Dep + 1), sz[u] += sz[e[u][i]];         if (sz[e[u][i]] > sz[son[u]]) son[u] = e[u][i];       }   }   void dfs2(int u, int Top) {     top[u] = Top;     dfn[u] = ++num;     idfn[num] = u;     if (son[u]) dfs2(son[u], Top);     for (register int i = (0); i <= (((int)e[u].size()) - 1); i++)       if (e[u][i] != fa[u] && e[u][i] != son[u]) dfs2(e[u][i], e[u][i]);   }   int getlca(int u, int v) {     while (top[u] != top[v]) {       if (dep[top[u]] < dep[top[v]]) swap(u, v);       u = fa[top[u]];     }     return dep[u] < dep[v] ? u : v;   }   int getpath(int u, int v, double t, int xs, double c) {     while (top[u] != top[v]) {       int x = fa[top[u]];       mrk[top[u]].push_back(make_pair(           dot(t, dfn[u]),           dot(t + xs * (dep[u] - dep[x]) / c, dfn[u] - (dep[u] - dep[x]))));       t += xs * (dep[u] - dep[x]) / c;       u = fa[top[u]];     }     return u;   }   int main() {     read(n);     read(m);     for (register int i = (1); i <= (n - 1); i++) {       int u, v;       read(u);       read(v);       e[u].push_back(v);       e[v].push_back(u);     }     dfs1(1, 0, 0);     dfs2(1, 1);     for (register int i = (1); i <= (m); i++) {       int T, C, u, v;       read(T);       read(C);       read(u);       read(v);       double t = T, c = C;       int lca = getlca(u, v);       int ori = u;       v = getpath(v, lca, t + (dep[u] + dep[v] - 2 * dep[lca]) * 1.0 / c, -1, c);       u = getpath(u, lca, t, 1, c);       t += (dep[ori] - dep[u]) * 1.0 / c;       if (dep[u] >= dep[v])         mrk[top[u]].push_back(make_pair(             dot(t, dfn[u]), dot(t + (dep[u] - dep[v]) * 1.0 / c, dfn[v])));       else         mrk[top[u]].push_back(make_pair(             dot(t, dfn[u]), dot(t + (dep[v] - dep[u]) * 1.0 / c, dfn[v])));     }     for (register int t = (1); t <= (n); t++)       if (((int)mrk[t].size())) {         Set.clear();         len = 0;         for (register int i = (0); i <= (((int)mrk[t].size()) - 1); i++)           len++, a[len] = mrk[t][i].first, b[len] = mrk[t][i].second;         for (register int i = (1); i <= (len); i++)           if (a[i].x > b[i].x) swap(a[i], b[i]);         for (register int i = (1); i <= (len); i++)           ev[2 * i - 1] = make_pair(a[i].x, i), ev[2 * i] = make_pair(b[i].x, -i);         sort(ev + 1, ev + len * 2 + 1, cmp1);         for (register int i = (1); i <= (len * 2); i++) {           if ((cur = ev[i].first) >= ans) break;           if (ev[i].second > 0) {             set<node>::iterator it = Set.insert((node){ev[i].second}).first, pre,                                 nxt;             pre = it;             nxt = it;             nxt++;             if (it != Set.begin()) {               pre--;               umin(ans, getans((*pre).u, (*it).u));             }             if (nxt != Set.end()) {               umin(ans, getans((*nxt).u, (*it).u));             }           } else {             set<node>::iterator it = Set.find((node){-ev[i].second}), it1, it2;             it1 = it, it2 = it;             it2++;             if (it != Set.begin() && it2 != Set.end()) {               it1--;               umin(ans, getans((*it1).u, (*it2).u));             }             Set.erase(it);           }         }       }     if (ans < 1e8)       printf( %.9lf n , ans);     else       puts( -1 );     return 0;   }   