#include "bits/stdc++.h"
using namespace std;
struct fenwick {
vector<int> tree;
int n;
void init(int len) {
n = len;
tree.assign(n + 1, 0);
}
void upd(int i, int v) { for (i++; i <= n; i += i & (-i)) tree[i] += v; }
int get(int i) {
int sum = 0;
for (i++; i > 0; i -= i & (-i)) sum += tree[i];
return sum;
}
int get(int l, int r) {
return get(r) - get(l - 1);
}
};
int main() {
cin.tie(0)->sync_with_stdio(false);
int n, q;
cin >> n >> q;
vector<vector<int>> g(2 * n);
for (int i = 1; i < n; i++) {
int u, v;
cin >> u >> v;
g[u].emplace_back(v);
g[v].emplace_back(u);
}
const int lg = 17;
vector jump(lg, vector(n + 1, 0));
vector<int> tin(n + 1), tout(n + 1), ord(n + 1);
vector<int> depth(n + 1), rem(n + 1);
vector<pair<int, int>> cnt(n + 1);
int ans = 0, z = 0, root = 1;
while (g[root].size() == 1) root++;
auto dfs = [&](auto &dfs, int u, int p) -> void {
for (int i = 1; i < lg; i++) {
jump[i][u] = jump[i - 1][jump[i - 1][u]];
if (!jump[i][u]) break;
}
tin[u] = tout[u] = z++;
ord[tin[u]] = u;
for (int v: g[u]) {
if (v == p) continue;
jump[0][v] = u;
depth[v] = depth[u] + 1;
dfs(dfs, v, u);
rem[u] += rem[v];
tout[u] = tout[v];
}
rem[u] = 2 - rem[u] % 2;
if (g[u].size() == 1) rem[u] = 1;
if (u != root) ans += rem[u];
};
dfs(dfs, root, 0);
auto dfs2 = [&](auto &dfs2, int u, int p) -> void {
for (int v: g[u]) {
if (v == p) continue;
cnt[v] = cnt[u];
if (rem[v] == 1) cnt[v].first++;
else cnt[v].second++;
dfs2(dfs2, v, u);
}
};
dfs2(dfs2, root, 0);
auto isPar = [&](int u, int v) -> bool { return tin[u] <= tin[v] and tout[v] <= tout[u]; };
auto lca = [&](int u, int v) -> int {
if (isPar(u, v)) return u;
if (isPar(v, u)) return v;
for (int i = lg - 1; i >= 0; i--) {
if (jump[i][u] and !isPar(jump[i][u], v)) u = jump[i][u];
}
return jump[0][u];
};
int old_ans = ans;
vector<int> shit(n + 1);
vector<bool> vis(n + 1);
fenwick fw; fw.init(n + 1);
while (q--) {
int ln;
cin >> ln;
ans = old_ans + ln;
vector<int> v(ln), vec;
for (int &x: v) cin >> x;
for (int x: v) shit[x]++;
for (int x: v) {
if (vis[x]) continue;
vis[x] = true;
if (g[x].size() == 1) shit[x]--;
if (shit[x] % 2) vec.emplace_back(x);
}
sort(vec.begin(), vec.end(), [&](int a, int b) {
return tin[a] < tin[b];
});
set<int> st;
for (int x: vec) st.insert(tin[x]), fw.upd(tin[x], 1);
for (int i = 1; i < vec.size(); i++) st.insert(tin[lca(vec[i - 1], vec[i])]);
auto dfs = [&](auto &dfs, int u, int p) -> void {
st.erase(tin[u]);
while (true) {
auto it = st.lower_bound(tin[u]);
if (it == st.end() or *it > tout[u]) break;
int v = ord[*it];
dfs(dfs, v, u);
}
if (fw.get(tin[u], tout[u]) % 2 == 0) return;
ans += (cnt[u].first - cnt[p].first) - (cnt[u].second - cnt[p].second);
};
// for (int x: st) cout << ord[x] << ' ' << x << ' ' << tout[ord[x]] << endl;
// for (int x: vec) cout << x << ' ' << tin[x] << ' ' << tout[x] << endl;
// cout << '\t' << st.size() << ' ' << vec.size() << endl;
while (!st.empty()) {
dfs(dfs, ord[*st.begin()], root);
}
// cout << st.size() << endl;
if ((fw.get(tin[root], tout[root]) + rem[root]) % 2) cout << "-1\n";
else cout << ans << '\n';
for (int x: v) shit[x] = vis[x] = 0;
for (int x: vec) fw.upd(tin[x], -1);
}
}
