#include <bits/stdc++.h> using namespace std; #define int long long #define pb push_back #define all(v) v.begin(), v.end() #define F first #define S second const int N = 100000; int lift[N][21]; vector<int> adj[N], level(N,0), dep(N,0), v(N,0), ans; map<pair<int,int>, int> E; int cnt = 0, n, m, k; void dfs(int node,int p){ level[node] = cnt++; dep[node] = (p == -1 ? 0 : dep[p] + 1); // ✔ FIX 1 lift[node][0] = p; for(auto go : adj[node]){ if(go != p) dfs(go, node); } } int dfsans(int node,int p){ int sm = v[node]; for(auto go : adj[node]){ if(go != p) sm += dfsans(go, node); } if(p != -1 && sm / 2 >= k){ // ✔ FIX 3 ans.pb(E[{min(node, p), max(node, p)}]); } return sm; } int LCA(int x,int y){ if (dep[x] < dep[y]) swap(x,y); int diff = dep[x] - dep[y]; for(int layer = 0; layer < 20; layer++){ if(diff & (1LL << layer)) x = lift[x][layer]; } if(x == y) return x; for(int layer = 19; layer >= 0; layer--){ if(lift[x][layer] != lift[y][layer]){ x = lift[x][layer]; y = lift[y][layer]; } } return lift[x][0]; } void calclift(){ for(int layer = 1; layer <= 19; layer++){ for(int i = 0; i < n; i++){ if (lift[i][layer-1] == -1) lift[i][layer] = -1; // ✔ FIX 2 else lift[i][layer] = lift[lift[i][layer-1]][layer-1]; } } } void _(){ cin >> n >> m >> k; for(int i = 1; i <= n - 1; i++){ int u,vv; cin >> u >> vv; u--,vv--; adj[u].pb(vv); adj[vv].pb(u); E[{min(u, vv), max(u, vv)}] = i; } dfs(0, -1); calclift(); while(m--){ int siz; cin >> siz; deque<int> nodes; for(int i = 0; i < siz; i++){ int x; cin >> x; x--; nodes.pb(x); } sort(all(nodes), [](int a, int b){ return level[a] < level[b]; }); int lowest = nodes[0]; for(int i = 1; i < siz; i++) lowest = LCA(lowest, nodes[i]); nodes.push_front(lowest); for(int i = 0; i < nodes.size(); i++){ int anc = LCA(nodes[i], nodes[(i + 1) % nodes.size()]); v[anc] -= 2; v[nodes[i]] += 1; v[nodes[(i + 1) % nodes.size()]] += 1; } } dfsans(0, -1); cout << ans.size() << endl; for(auto pr : ans) cout << pr << " "; cout << endl; } int32_t main(){ int t = 1; while(t--) _(); return 0; }