#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;
vector <int> g[N];
int leaves;
int sz[N], big[N], in[N], head[N], hl[N], par[N], num, ti;
void dfs(int u, int p) {
sz[u] = 1;
par[u] = p;
for (auto v: g[u]) {
if (v == p) continue;
dfs(v, u);
sz[u] += sz[v];
if (sz[v] >= sz[big[u]]) big[u] = v;
}
}
void hld(int u, int p) {
in[u] = ++ti;
if (big[u]) {
int v = big[u];
hl[v] = hl[u];
head[v] = head[u];
hld(v, u);
}
for (auto v: g[u]) {
if (v == p || v == big[u]) continue;
hl[v] = ++num;
head[v] = v;
hld(v, u);
}
}
int vis[N];
int st[N * 4], lazy[N * 4];
void push(int id, int len) {
lazy[id] ^= 1;
st[id] = len - st[id];
}
void modify(int id, int L, int R, int u, int v) {
if (u > R || L > v) return;
if (u <= L && R <= v) {
push(id, R - L + 1);
return;
}
int mid = L + R >> 1;
if (lazy[id]) {
push(id * 2, mid - L + 1);
push(id * 2 + 1, R - mid);
lazy[id] = 0;
}
modify(id * 2, L, mid, u, v);
modify(id * 2 + 1, mid + 1, R, u, v);
st[id] = st[id * 2] + st[id * 2 + 1];
}
void solve() {
++ti;
int m;
cin >> m;
vector <int> s, rev;
int l = leaves + m;
while (m--) {
int u;
cin >> u;
if (g[u].size() <= 1 && vis[u] != ti) {
--l;
vis[u] = ti;
rev.push_back(u);
}
s.push_back(u);
}
if (l % 2) {
cout << -1 << '\n';
return;
}
for (auto u: rev)
for (; u; u = par[head[u]]) modify(1, 1, n, in[head[u]], in[u]);
for (auto u: s)
for (; u; u = par[head[u]]) modify(1, 1, n, in[head[u]], in[u]);
int _1 = st[1] + s.size();
int _2 = (n - 1 - st[1]);
cout << _1 + _2 * 2 << '\n';
for (auto u: s)
for (; u; u = par[head[u]]) modify(1, 1, n, in[head[u]], in[u]);
for (auto u: rev)
for (; u; u = par[head[u]]) modify(1, 1, n, in[head[u]], in[u]);
}
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].push_back(v);
g[v].push_back(u);
}
int r = 1;
for (int i = 1; i <= n; ++i)
if (g[i].size() > 1) r = i;
dfs(r, 0);
hl[r] = ++num;
head[r] = r;
hld(r, 0);
for (int i = 1; i <= n; ++i)
if (g[i].size() <= 1) {
++leaves;
for (int u = i; u; u = par[head[u]]) modify(1, 1, n, in[head[u]], in[u]);
}
while (q--) solve();
}
