#include <bits/stdc++.h>
using namespace std;
struct node {
int cnt1 = 0;
int cnt2 = 0;
};
struct st {
vector<node> v;
vector<bool> lazy;
int as;
};
node merge (node &l, node &r) {
return {l.cnt1 + r.cnt1, l.cnt2 + r.cnt2};
}
void push (st &seg, int i) {
if (seg.lazy[i]) {
int l = i*2;
int r = i*2 + 1;
seg.lazy[l] = !seg.lazy[l];
seg.lazy[r] = !seg.lazy[r];
swap(seg.v[l].cnt1, seg.v[l].cnt2);
swap(seg.v[r].cnt1, seg.v[r].cnt2);
seg.lazy[i] = false;
}
}
st build (vector<node> vs) {
int n = vs.size();
int as = 1 << (1 + __lg(n));
vector<node> v (as*2);
for (int i = 0; i < n; i++) {
v[as + i] = vs[i];
}
for (int i = as-1; i > 0; i--) {
v[i] = merge(v[i*2], v[i*2 + 1]);
}
vector<bool> lazy (as*2, false);
return {v, lazy, as};
}
void apply (st &seg, int l, int r, int i = 1, int lo = 0, int hi = -1) {
if (hi == -1) hi = seg.as;
if (lo >= r || hi <= l) return;
if (l <= lo && hi <= r) {
swap(seg.v[i].cnt1, seg.v[i].cnt2);
seg.lazy[i] = !seg.lazy[i];
return;
}
push(seg, i);
int mid = (lo + hi) / 2;
apply(seg, l, r, i*2, lo, mid);
apply(seg, l, r, i*2 + 1, mid, hi);
seg.v[i] = merge(seg.v[i*2], seg.v[i*2 + 1]);
}
vector<vector<int>> adj_list;
vector<int> par;
vector<bool> leaf;
vector<int> depth, sz;
vector<node> vs;
vector<int> leaf_cnt;
int dfscnt = 0;
vector<int> pos, head;
st seg;
void dfs1 (int v) {
leaf[v] = adj_list[v].size() == 1;
sz[v] = 1;
int max_sz = -1;
for (auto &it : adj_list[v]) {
if (it == par[v]) continue;
par[it] = v;
depth[it] = depth[v] + 1;
dfs1 (it);
sz[v] += sz[it];
leaf_cnt[v] += leaf_cnt[it];
if (sz[it] > max_sz) {
max_sz = sz[it];
swap(it, adj_list[v][0]);
}
}
if (leaf[v]) leaf_cnt[v]++;
if (leaf_cnt[v] % 2 == 0) vs[v].cnt2++;
else vs[v].cnt1++;
}
void dfs2 (int v) {
pos[v] = dfscnt++;
for (int i = 0; i < adj_list[v].size(); i++) {
int it = adj_list[v][i];
if (it == par[v]) continue;
if (i == 0) {
head[it] = head[v];
} else {
head[it] = it;
}
dfs2 (it);
}
}
void invert (int a) {
while (a != -1) {
apply(seg, pos[head[a]], pos[a]+1);
a = par[head[a]];
}
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int n, q;
cin >> n >> q;
adj_list = vector<vector<int>> (n);
for (int i = 0; i < n-1; i++) {
int u, v;
cin >> u >> v;
adj_list[u-1].push_back(v-1);
adj_list[v-1].push_back(u-1);
}
vector<vector<int>> va (q);
for (int i = 0; i < q; i++) {
int d;
cin >> d;
for (int j = 0; j < d; j++) {
int a;
cin >> a;
va[i].push_back(a-1);
}
}
par = vector<int> (n, -1);
leaf = vector<bool> (n, false);
depth = vector<int> (n, 0);
sz = vector<int> (n, 1);
vs = vector<node> (n);
leaf_cnt = vector<int> (n, 0);
dfs1 (0);
pos = vector<int> (n, 0);
head = vector<int> (n, 0);
dfs2 (0);
vs[0] = {};
vector<node> vsp (n);
for (int i = 0; i < n; i++) {
vsp[pos[i]] = vs[i];
}
seg = build(vsp);
vector<int> nleafs (n, 0);
int lc = leaf_cnt[0];
for (int i = 0; i < q; i++) {
for (int j = 0; j < va[i].size(); j++) {
int v = va[i][j];
if (!leaf[v] || nleafs[v] > 0) {
lc++;
invert(v);
}
nleafs[v]++;
}
int sol = seg.v[1].cnt1 + seg.v[1].cnt2 * 2 + va[i].size();
if (lc % 2 == 1) sol = -1;
cout << sol << "\n";
for (int j = 0; j < va[i].size(); j++) {
int v = va[i][j];
if (!leaf[v] || nleafs[v] > 1) {
lc--;
invert(v);
}
nleafs[v]--;
}
}
return 0;
}
