#include <bits/stdc++.h>
#define ll long long
using namespace std;
struct T {
int v;
int tinV;
bool operator<(const auto& o) const {
return tinV < o.tinV;
}
};
int n,m,k;
vector<vector<pair<int, int>>> adj;
vector<int> edgeToP;
vector<vector<T>> chosenC;
vector<int> countS;
int l;
int timer;
vector<int> tin, tout;
vector<vector<int>> up;
vector<int> pathPre;
vector<int> pathPrefix;
void dfs(int u, int p) {
tin[u] = timer++;
up[u][0] = p;
for (int i = 1; i <= l; i++) {
up[u][i] = up[up[u][i-1]][i-1];
}
for (const auto& v : adj[u]) {
if (v.first != p) {
edgeToP[v.first] = v.second;
dfs(v.first, u);
}
}
tout[u] = timer++;
}
bool isAncestor(int u, int v) {
return tin[u] <= tin[v] && tout[u] >= tout[v];
}
int lca(int u, int v) {
if (isAncestor(u,v)) return u;
if (isAncestor(v,u)) return v;
for (int i = l; i >= 0; i--) {
if (!isAncestor(up[u][i], v)) u = up[u][i];
}
return up[u][0];
}
void preprocess(int root) {
tin.resize(n+1);
tout.resize(n+1);
timer = 0;
l = ceil(log2(n)); if (l == 0) l = 1;
up.assign(n+1, vector<int>(l+1));
dfs(root, root);
}
int dfsSubtree(int u, int p) {
int sum = pathPre[u];
for (const auto& v : adj[u]) {
if (v.first != p) sum += dfsSubtree(v.first, u);
}
pathPrefix[u] = sum;
return sum;
}
int main() {
scanf("%d %d %d",&n,&m,&k);
adj.resize(n+1, {});
edgeToP.resize(n+1, -1);
countS.resize(n, 0);
chosenC.resize(m+1, {});
for (int i = 1; i < n; i++) {
int a,b; scanf("%d %d",&a,&b);
adj[a].push_back({b, i});
adj[b].push_back({a, i});
}
preprocess(1);
for (int i = 1; i <= m; i++) {
int s; scanf("%d",&s);
for (int j = 0; j < s; j++) {
int z; scanf("%d",&z);
chosenC[i].push_back({z, tin[z]});
}
}
pathPre.resize(n+1, 0);
for (int i = 1; i <= m; i++) {
// dfs sortierung mit tin
sort(chosenC[i].begin(), chosenC[i].end());
for (int j = 0; j < chosenC[i].size(); j++) {
// make paths form u1 -> u2, u2->u3 , ..., un -> u1
int a = chosenC[i][j].v;
int b = chosenC[i][(j+1)%chosenC[i].size()].v;
pathPre[a]++;
pathPre[b]++;
pathPre[lca(a,b)] -= 2;
}
}
// subtree (only count if val/2 >= k)
pathPrefix.resize(n+1, -1);
dfsSubtree(1, -1);
set<int> addRails;
for (int i = 1; i <= n; i++) {
if (pathPrefix[i] / 2 >= k) addRails.insert(i);
}
printf("%d \n", addRails.size());
for (const auto& a : addRails) printf("%d ", edgeToP[a]);
return 0;
}
