#include <bits/stdc++.h>
using namespace std;
const int MAXN = 100001;
vector<int> g[MAXN];
int tree[2 * MAXN], depth[MAXN], parent[MAXN], pos[MAXN], head[MAXN], heavy[MAXN], timer = 0, n, q, leaf[MAXN];
int dfs(int u, int d) {
depth[u] = d;
int s = 1, max_s = 0;
for (int v : g[u]) {
if (v != parent[u]) {
parent[v] = u;
int k = dfs(v, d + 1);
s += k;
if (k > max_s) {
max_s = k;
heavy[u] = v;
}
}
}
return s;
}
void decomp(int u, int h) {
head[u] = h;
pos[u] = ++timer;
if (heavy[u])
decomp(heavy[u], h);
for (int v : g[u]) {
if (v != parent[u] && v != heavy[u])
decomp(v, v);
}
}
int qry(int u) {
u = n + pos[u];
int res = tree[u];
for (u /= 2; u >= 1; u /= 2) {
res ^= tree[u];
}
return res;
}
void segupd(int l, int r) {
l += n; r += n;
while (l <= r) {
if (l % 2 == 1) tree[l++] ^= 1;
if (r % 2 == 0) tree[r--] ^= 1;
l /= 2; r /= 2;
}
}
void upd(int a, int b) {
for (; head[a] != head[b]; b = parent[head[b]]) {
if (depth[head[a]] > depth[head[b]])
swap(a, b);
segupd(pos[head[b]], pos[b]);
}
if (depth[a] > depth[b])
swap(a, b);
segupd(pos[a], pos[b]);
}
int main() {
ios::sync_with_stdio(0); cin.tie(0);
cin >> n >> q;
for (int i = 0; i < n - 1; i++) {
int a, b; cin >> a >> b;
g[a].push_back(b);
g[b].push_back(a);
}
dfs(1, 0);
decomp(1, 1);
for (int i = 1; i <= n; i++) {
leaf[i] = g[i].size() == 1;
if (leaf[i]) upd(1, i);
}
while (q--) {
int c; cin >> c;
vector<int> v(c);
for (int i = 0; i < c; i++) {
cin >> v[i];
if (leaf[v[i]] == 1) {
leaf[v[i]] = 2;
} else {
upd(1, v[i]);
}
}
if (qry(1) == 1) {
cout << "-1\n";
} else {
int ans = n - 1 + c;
for (int i = 2; i <= n; i++) {
if (qry(i) == 0) ans++;
}
cout << ans << "\n";
}
for (int i = 0; i < c; i++) {
if (leaf[v[i]] == 2) {
leaf[v[i]] = 1;
} else {
upd(1, v[i]);
}
}
}
}
