#include <bits/stdc++.h>
#define ll long long
using namespace std;
struct T {
ll v;
ll tinV;
bool operator<(const T& o) const {
return tinV < o.tinV;
}
};
ll n,m,k;
vector<vector<pair<ll, ll>>> adj;
vector<ll> edgeToP;
vector<vector<T>> chosenC;
vector<ll> countS;
ll l;
ll timer;
vector<ll> tin, tout;
vector<vector<ll>> up;
vector<ll> pathPre;
vector<ll> pathPrefix;
void dfs(ll u, ll p) {
tin[u] = timer++;
up[u][0] = p;
for (ll 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(ll u, ll v) {
return tin[u] <= tin[v] && tout[u] >= tout[v];
}
ll lca(ll u, ll v) {
if (isAncestor(u,v)) return u;
if (isAncestor(v,u)) return v;
for (ll i = l; i >= 0; i--) {
if (!isAncestor(up[u][i], v)) u = up[u][i];
}
return up[u][0];
}
void preprocess(ll 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<ll>(l+1));
dfs(root, root);
}
ll dfsSubtree(ll u, ll p) {
ll 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("%lld %lld %lld",&n,&m,&k);
adj.resize(n+1, {});
edgeToP.resize(n+1, -1);
countS.resize(n, 0);
chosenC.resize(m+1, {});
for (ll i = 1; i < n; i++) {
ll a,b; scanf("%lld %lld",&a,&b);
adj[a].push_back({b, i});
adj[b].push_back({a, i});
}
preprocess(1);
for (ll i = 1; i <= m; i++) {
ll s; scanf("%lld",&s);
for (ll j = 0; j < s; j++) {
ll z; scanf("%lld",&z);
chosenC[i].push_back({z, tin[z]});
}
}
pathPre.resize(n+1, 0);
for (ll i = 1; i <= m; i++) {
// dfs sortierung mit tin
sort(chosenC[i].begin(), chosenC[i].end());
for (ll j = 0; j < chosenC[i].size(); j++) {
// make paths form u1 -> u2, u2->u3 , ..., un -> u1
ll a = chosenC[i][j].v;
ll 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<ll> addRails;
for (ll i = 2; i <= n; i++) {
if (pathPrefix[i] / 2 >= k) addRails.insert(i);
}
// printf("%zu \n", addRails.size());
printf("%lld \n", (ll)addRails.size());
for (const auto& a : addRails) printf("%lld ", edgeToP[a]);
// (can you do that for every m and compute at subtrees at end and then half everything or do you have to do before?)
// subtree sum and then half
return 0;
}
