func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 20005;   const int M = 400005;   vector<pair<int, int> > E[N];   int dep[N], fa[N][16], fav[N][16];   int n, m, S, T, nd, jud[N * 2];   int head[M], vis[M], tot = 1;   int dis[M], q[M];   struct edge {     int to, next, f;   } e[M * 5];   void add(int x, int y, int f) {     e[++tot] = (edge){y, head[x], f};     head[x] = tot;     e[++tot] = (edge){x, head[y], 0};     head[y] = tot;   }   bool bfs() {     for (int i = (int)(1); i <= (int)(nd); i++) dis[i] = -1;     int h = 0, t = 1;     q[1] = S;     dis[S] = 0;     while (h != t) {       int x = q[++h];       for (int i = head[x]; i; i = e[i].next)         if (dis[e[i].to] == -1 && e[i].f) {           dis[e[i].to] = dis[x] + 1;           if (e[i].to == T) return 1;           q[++t] = e[i].to;         }     }     return 0;   }   int dfs(int x, int flow) {     if (x == T) return flow;     int k, rest = flow;     for (int i = head[x]; i && rest; i = e[i].next)       if (dis[e[i].to] == dis[x] + 1 && e[i].f) {         k = dfs(e[i].to, min(rest, e[i].f));         e[i].f -= k;         e[i ^ 1].f += k;         rest -= k;       }     if (rest) dis[x] = -1;     return flow - rest;   }   void dfs(int x) {     for (auto i : E[x])       if (i.first != fa[x][0]) {         dep[i.first] = dep[x] + 1;         fa[i.first][0] = x;         fav[i.first][0] = i.second;         dfs(i.first);       }   }   int LCA(int x, int y) {     if (dep[x] < dep[y]) swap(x, y);     int tmp = dep[x] - dep[y];     for (int i = (int)(14); i >= (int)(0); i--)       if (tmp & (1 << i)) x = fa[x][i];     for (int i = (int)(14); i >= (int)(0); i--)       if (fa[x][i] != fa[y][i]) x = fa[x][i], y = fa[y][i];     return x == y ? x : fa[x][0];   }   int main() {     scanf( %d%d , &n, &m);     for (int i = (int)(1); i <= (int)(n - 1); i++) {       int x, y;       scanf( %d%d , &x, &y);       E[x].push_back(pair<int, int>(y, i));       E[y].push_back(pair<int, int>(x, i));     }     S = nd = n;     T = ++nd;     for (int i = (int)(1); i <= (int)(n - 1); i++) add(S, i, 1), jud[i] = tot;     for (int i = (int)(1); i <= (int)(m); i++) add(++nd, T, 1), jud[i + n] = tot;     dfs(1);     for (int i = (int)(1); i <= (int)(14); i++)       for (int j = (int)(1); j <= (int)(n); j++) {         fa[j][i] = fa[fa[j][i - 1]][i - 1];         if (dep[j] >= 1 << i) {           fav[j][i] = ++nd;           add(fav[j][i - 1], fav[j][i], 1 << 30);           add(fav[fa[j][i - 1]][i - 1], fav[j][i], 1 << 30);         }       }     for (int i = (int)(1); i <= (int)(m); i++) {       int p = n + 1 + i, x, y;       scanf( %d%d , &x, &y);       int L = LCA(x, y);       for (int j = (int)(14); j >= (int)(0); j--) {         if (dep[x] - dep[L] >= 1 << j)           add(fav[x][j], n + 1 + i, 1 << 30), x = fa[x][j];         if (dep[y] - dep[L] >= 1 << j)           add(fav[y][j], n + 1 + i, 1 << 30), y = fa[y][j];       }       assert(x == L && y == L);     }     int tmp = 0;     for (; bfs(); tmp += dfs(S, 1 << 30))       ;     vector<int> ans1, ans2;     for (int i = (int)(1); i <= (int)(n - 1); i++)       if (dis[i] == -1) ans1.push_back(i);     for (int i = (int)(1); i <= (int)(m); i++)       if (dis[i + n + 1] != -1) ans2.push_back(i);     assert(ans1.size() + ans2.size() == tmp);     printf( %d n , ans1.size() + ans2.size());     printf( %d  , ans2.size());     for (auto i : ans2) printf( %d  , i);     puts(  );     printf( %d  , ans1.size());     for (auto i : ans1) printf( %d  , i);     puts(  );   }   