#pragma GCC optimize("Ofast,unroll-loops")
// #pragma comment(linker, "/stack:200000000")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,fma,tune=native")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef int ll;
typedef long double ld;
typedef pair <ll, ll> pll;
#ifdef SINA
#define dbg(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1> void __f(const char* name, Arg1&& arg1) { cout << name << " : " << arg1 << std::endl; }
template <typename Arg1, typename... Args> void __f (const char* names, Arg1&& arg1, Args&&... args) {
const char* comma = strchr(names + 1, ',');cout.write(names, comma - names) << " : " << arg1<<" | ";__f(comma+1, args...); }
#define dbg2(x, j, n) cout<< #x << " : "; output((j), (n), x, 1); cout.flush();
#else
#define dbg(...) 0
#define dbg2(x, j, n) 0
#endif
#define SZ(x) ((ll)((x).size()))
#define File(s, t) freopen(s ".txt", "r", stdin); freopen(t ".txt", "w", stdout);
#define input(j, n, a) for (int _i = (j); _i < (n)+(j); _i++) cin>> a[_i];
#define output(j, n, a, t) for (int _i = (j); _i < (n)+(j); _i++) cout<< a[_i] << (((t) && _i != (n)+(j)-1)? ' ' : '\n');
#define kill(x) return cout<< (x) << endl, 0
#define cl const ll
#define fr first
#define sc second
#define lc (v << 1)
#define rc (lc | 1)
#define mid ((l + r) >> 1)
#define All(x) (x).begin(), (x).end()
cl inf = sizeof(ll) == 4 ? (1e9 + 10) : (3e18), mod = 1e9 + 7, MOD = 998244353;
template <class A,class B> ostream& operator << (ostream& out,const pair<A,B>&a){return out<<'('<<a.first<<", "<<a.second<<')';}
template <class A> ostream& operator << (ostream& out, const vector<A> &a) {
out<< '['; for (int i = -1; ++i < int(a.size());) out<< a[i] << (i + 1 < int(a.size()) ? ", " : ""); return out<<']'; }
template <class T, typename _t = less <T> > using Tree = tree <T, null_type, _t, rb_tree_tag, tree_order_statistics_node_update>;
cl N = 1e5 + 7, lg = 17;
ll tin [N], tout [N], anc [N][lg], h [N], par [N], lz [N], T, n, q, k;
vector <pll> adj [N];
vector <ll> vec, stk;
void DFS (cl &v = 1, cl &pr = 1) {
tin[v] = ++T;
h[v] = h[pr] + 1;
anc[v][0] = pr;
for (ll i = 1; i < lg; i++) anc[v][i] = anc[anc[v][i - 1]][i - 1];
for (auto &u : adj[v]) if (u.fr != pr) DFS(u.fr, v);
tout[v] = T;
}
inline ll up (ll v, cl &d) { for (ll i = lg; i--;) if (d >> i & 1) v = anc[v][i]; return v; }
inline ll LCA (ll v, ll u) {
if (h[v] > h[u]) swap(v, u);
u = up(u, h[u] - h[v]);
if (v == u) return v;
for (ll i = lg; i--;) if (anc[v][i] ^ anc[u][i]) v = anc[v][i], u = anc[u][i];
return anc[v][0];
}
void add (ll s) {
sort(All(vec), [&](cl &v, cl &u) { return tin[v] < tin[u]; });
for (ll i = 1; i < s; i++) vec.push_back(LCA(vec[i - 1], vec[i]));
sort(All(vec), [&](cl &v, cl &u) { return tin[v] < tin[u]; });
vec.resize(unique(All(vec)) - vec.begin());
stk.clear();
for (auto &v : vec) {
while (!stk.empty() && !(tin[stk.back()] <= tin[v] && tout[v] <= tout[stk.back()])) stk.pop_back();
if (!stk.empty()) par[v] = stk.back();
else par[v] = -1;
stk.push_back(v);
}
for (auto &v : vec) if (par[v] != -1) lz[v]++, lz[par[v]]--;
}
ll dfs (cl &v = 1, cl &ep = 0) {
for (auto &u : adj[v]) if (u.fr != anc[v][0]) lz[v] += dfs(u.fr, u.sc);
if (ep && lz[v] >= k) vec.push_back(ep);
return lz[v];
}
int main ()
{
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin>> n >> q >> k;
for (ll i = 1, v, u; i < n; i++) {
cin>> v >> u;
adj[v].push_back({u, i});
adj[u].push_back({v, i});
}
DFS();
for (ll s; q--;) {
cin>> s;
vec.resize(s);
for (auto &x : vec) cin>> x;
add(s);
}
vec.clear();
dfs();
sort(All(vec));
cout<< SZ(vec) << '\n';
for (auto &x : vec) cout<< x << ' '; cout<< '\n';
cerr<< "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
return 0;
}
/*
6 3 2
1 3
2 3
3 4
6 4
4 5
4 1 3 2 5
2 6 3
2 3 2
*/
