#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
inline void debugMode() {
#ifndef ONLINE_JUDGE
freopen("in.txt", "r", stdin);
freopen("out.txt", "w", stdout);
#endif // ONLINE_JUDGE
}
const int N = 1e5 + 10;
vector<int> v[N];
int n, q;
int c[N], add[N];
int res, root;
void dfs(int x, int p) {
if (add[x] == 0) {
c[x] = (v[x].size() == 1);
} else {
res += add[x];
c[x] = add[x];
}
for (auto to : v[x]) {
if (to == p)
continue;
dfs(to, x);
c[x] += c[to];
}
// cout << "x: " << x << " " << c[x] << "\n";
if (x != root)
res += (c[x] % 2 == 1 ? 1 : 2);
}
void solve() {
cin >> n >> q;
for (int i = 0; i < n - 1; i++) {
int a, b;
cin >> a >> b;
v[a].push_back(b);
v[b].push_back(a);
}
for (int i = 1; i <= n; i++) {
if (v[i].size() > 1) {
root = i;
break;
}
}
// cout << root << "\n";
while (q--) {
int d;
cin >> d;
vector<int> g(d);
int nw = n;
for (auto &i : g) {
cin >> i;
add[i]++;
}
res = 0;
dfs(root, root);
cout << (c[root] % 2 == 1 ? -1 : res) << "\n";
for (auto i : g) {
add[i] = 0;
}
}
}
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
// debugMode();
int $ = 1;
// cin >> $;
while ($--) {
solve();
}
}
