#include <bits/stdc++.h>
using namespace std;
#define int long long
constexpr int maxn = 400001;
int n, q, d[maxn], in[maxn], jump[18][maxn], parity[maxn], prf[maxn], tim, ans;
vector<int> adj[maxn], vrt[maxn];
bool vis[maxn], markNode[maxn];
int addcnt[maxn];
int dfs(int v) {
in[v] = tim++;
vis[v] = 1;
int num = 0;
if ((int)adj[v].size() == 1) num = 1;
for (int u : adj[v]) {
if (!vis[u]) {
jump[0][u] = v;
d[u] = d[v] + 1;
int x = dfs(u);
ans += x;
num += x;
}
}
parity[v] = (num % 2 ? 1 : -1);
return 2 - num % 2;
}
void calc(int v, int cur) {
vis[v] = 1;
prf[v] = cur;
for (int u : adj[v]) if (!vis[u]) calc(u, cur + parity[u]);
}
int rt;
void build() {
jump[0][rt] = rt;
for (int i = 1; i < 18; i++) {
for (int j = 1; j <= n; j++) jump[i][j] = jump[i - 1][jump[i - 1][j]];
}
}
int lca(int v, int u) {
if (v == u) return v;
if (d[v] > d[u]) swap(u, v);
int t = d[u] - d[v];
for (int k = 17; k >= 0; k--) {
if (((1LL << k) & t)) u = jump[k][u];
}
if (v == u) return v;
for (int k = 17; k >= 0; k--) {
if (jump[k][v] != jump[k][u]) v = jump[k][v], u = jump[k][u];
}
return jump[0][v];
}
int cnt;
int solve_vtree(int v) {
int odd = markNode[v];
for (int u : vrt[v]) {
int x = solve_vtree(u);
if (x) cnt += prf[u] - prf[v];
odd ^= x;
}
return odd;
}
signed main() {
cin.tie(0)->sync_with_stdio(0);
cin >> n >> q;
for (int i = 1; i < n; i++) {
int u, v; cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
int originalLeaves = 0;
for (int i = 1; i <= n; i++) {
if ((int)adj[i].size() == 1) originalLeaves++;
if ((int)adj[i].size() > 1) rt = i;
}
dfs(rt);
memset(vis, 0, sizeof vis);
calc(rt, 0);
memset(vis, 0, sizeof vis);
build();
while (q--) {
int t; cin >> t;
vector<int> touched;
cnt = t; // each added leaf-edge contributes 1
for (int i = 0; i < t; i++) {
int x; cin >> x;
if (addcnt[x] == 0) touched.push_back(x);
addcnt[x]++;
}
int leafCnt = originalLeaves + t;
vector<pair<int, int>> nodes;
for (int x : touched) {
bool wasLeaf = ((int)adj[x].size() == 1);
if (wasLeaf) leafCnt--; // the old original leaf x stops being a leaf once
int deltaLeaves = addcnt[x] - (wasLeaf ? 1 : 0);
if (deltaLeaves & 1) {
markNode[x] = 1;
nodes.push_back({in[x], x});
}
}
if (leafCnt % 2) {
cout << "-1\n";
for (int x : touched) {
addcnt[x] = 0;
markNode[x] = 0;
}
continue;
}
if (!nodes.empty()) {
sort(nodes.begin(), nodes.end());
int sz = nodes.size();
for (int i = 0; i + 1 < sz; i++) {
int w = lca(nodes[i].second, nodes[i + 1].second);
nodes.push_back({in[w], w});
}
}
nodes.push_back({in[rt], rt});
sort(nodes.begin(), nodes.end());
nodes.erase(unique(nodes.begin(), nodes.end(), [](auto a, auto b) {
return a.second == b.second;
}), nodes.end());
vector<int> st;
st.push_back(rt);
for (int i = 1; i < (int)nodes.size(); i++) {
int x = nodes[i].second;
while (!st.empty() && lca(st.back(), x) != st.back()) st.pop_back();
vrt[st.back()].push_back(x);
st.push_back(x);
}
solve_vtree(rt);
cout << ans + cnt << '\n';
for (auto [_, x] : nodes) vrt[x].clear();
for (int x : touched) {
addcnt[x] = 0;
markNode[x] = 0;
}
}
}
