#include <bits/stdc++.h>
using namespace std;
pair<long long, long long> dp[200005];
long long p[200005], leaf[200005];
vector<long long> adj[200005], vv;
void dfs(long long x)
{
dp[x]=make_pair(0LL, 0LL);
if (adj[x].size()==1) {leaf[x]=1;}
else {leaf[x]=0;};
for (auto y: adj[x])
{
if (y!=p[x])
{
p[y]=x;
dfs(y);
dp[x].first+=dp[y].first+dp[y].second;
dp[x].second+=dp[y].second;
dp[x].second%=2;
if (dp[x].second==0) {dp[x].second=2;};
};
};
if (x>1 && leaf[x]) {dp[x].second=1;};
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
long long n, q, i, u, v;
cin >> n >> q;
for (i=1; i<n; i++)
{
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
};
dfs(1);
while (q--)
{
cin >> i;
v=n+1;
while (i--)
{
cin >> u;
vv.push_back(u);
adj[u].push_back(v);
adj[v].push_back(u);
v++;
};
dfs(1);
if (leaf[1]==1 && dp[1].second==2) {cout << -1 << "\n";}
else if (leaf[1]==0 && dp[1].second==1) {cout << -1 << "\n";}
else {cout << dp[1].first << "\n";};
while (!vv.empty())
{
adj[adj[vv.back()].back()].pop_back();
adj[vv.back()].pop_back();
vv.pop_back();
};
};
}
