#include <bits/stdc++.h>
#pragma GCC optimize ("O3")
#pragma GCC optimize ("unroll-loops")
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
template <typename T>
using ordered_set = tree <T, null_type, less <T>, rb_tree_tag, tree_order_statistics_node_update>;
const int N = 1e5 + 10;
int n, q, ans;
set <int> g[N];
int sz[N];
void dfs(int u, int p) {
if (g[u].size() <= 1 && p) {
sz[u] = 1;
return;
}
sz[u] = 0;
for (auto v: g[u]) {
if (v == p) continue;
dfs(v, u);
sz[u] += sz[v];
ans += (sz[v] % 2 ? 1 : 2);
}
}
void solve() {
int m;
cin >> m;
for (int i = 1; i <= m; ++i) {
int u;
cin >> u;
g[u].insert(i + n);
g[i + n].insert(u);
}
int leaves = 0;
for (int i = 1; i <= n + m; ++i)
if (g[i].size() <= 1) ++leaves;
if (leaves % 2 == 0) {
dfs(1, 0);
cout << ans << '\n';
} else cout << -1 << '\n';
for (int u = n + 1; u <= n + m; ++u) {
for (auto v: g[u]) g[v].erase(u);
g[u].clear();
}
ans = 0;
}
int main() {
ios :: sync_with_stdio(0); cin.tie(0);
cin >> n >> q;
for (int i = 1; i < n; ++i) {
int u, v;
cin >> u >> v;
g[u].insert(v);
g[v].insert(u);
}
while (q--) solve();
}
