#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll MAXN = 2e5 + 5;
ll n, q, cnt, root, query[MAXN];
bool parity[MAXN];
vector<ll> adjl[MAXN];
void dfs(ll now, ll par, ll* ans) {
parity[now] = 0;
bool isLeaf = (adjl[now].size() == 1);
if(isLeaf) {parity[now] = 1;}
else {
for(ll nxt : adjl[now]) {
if(nxt == par) {continue ;}
dfs(nxt, now, ans);
parity[now] ^= parity[nxt];
}
}
if(parity[now] == 0) {(*ans)++;}
}
void solve() {
ll ans = cnt-1;
dfs(root, root, &ans);
if(parity[root] == 1) {
cout << "-1\n";
return ;
}
cout << (ans-1) << "\n";
return ;
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(0);
cin >> n >> q;
cnt = n;
for (int i = 0; i < n-1; ++i) {
ll a, b;
cin >> a >> b;
adjl[a].push_back(b);
adjl[b].push_back(a);
if(adjl[a].size() > 1) {root = a;}
else if(adjl[b].size() > 1) {root = b;}
}
while(q--) {
// Input
ll d;
cin >> d;
for (int i = 0; i < d; ++i) {
cin >> query[i];
cnt++;
adjl[cnt].push_back(query[i]);
adjl[query[i]].push_back(cnt);
}
solve();
// Reset
for (int i = 0; i < d; ++i) {
adjl[n+i+1].clear();
adjl[query[i]].pop_back();
}
cnt = n;
}
return 0;
}
