#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
const int MaxN = 1e6 + 5;
int n, q;
vector<int> graph[MaxN];
void Inp()
{
cin >> n >> q;
for (int x = 1; x < n; x++)
{
int u, v;
cin >> u >> v;
graph[u].push_back(v);
graph[v].push_back(u);
}
}
int root;
int Pre[MaxN];
int h[MaxN];
int par[MaxN];
int nxt[MaxN];
int sz[MaxN];
void PreDFS(int u, int p)
{
Pre[u] = ((int)graph[u].size() == 1);
nxt[u] = -1;
sz[u] = 1;
for (int x : graph[u])
{
if (x != p)
{
h[x] = h[u] + 1;
par[x] = u;
PreDFS(x, u);
Pre[u] ^= Pre[x];
sz[u] += sz[x];
if (nxt[u] == -1 || sz[nxt[u]] < sz[x])
{
nxt[u] = x;
}
}
}
}
int CurChain, CurPos;
int ChainHead[MaxN];
int ChainID[MaxN];
int Pos[MaxN];
int Arr[MaxN];
void HLD(int u, int p)
{
if (ChainHead[CurChain] == 0)
{
ChainHead[CurChain] = u;
}
ChainID[u] = CurChain;
Pos[u] = CurPos;
Arr[CurPos] = u;
CurPos++;
if (nxt[u] != -1)
{
HLD(nxt[u], u);
}
for (int x : graph[u])
{
if (x != p && x != nxt[u])
{
CurChain++;
HLD(x, u);
}
}
}
struct Node
{
int cnt0, cnt1, sum;
Node() = default;
Node(int _cnt0, int _cnt1, int _sum)
{
cnt0 = _cnt0;
cnt1 = _cnt1;
sum = _sum;
}
Node& operator = (const Node& other)
{
this->cnt0 = other.cnt0;
this->cnt1 = other.cnt1;
this->sum = other.sum;
return *this;
}
Node operator * (const Node& other) const
{
Node res;
res.cnt0 = this->cnt0 + other.cnt0;
res.cnt1 = this->cnt1 + other.cnt1;
res.sum = this->sum + other.sum;
return res;
}
};
Node SegTree[4 * MaxN];
int Lazy[4 * MaxN];
void Fix(int id, int l, int r)
{
if (Lazy[id] == 0)
{
return;
}
swap(SegTree[id].cnt0, SegTree[id].cnt1);
SegTree[id].sum = SegTree[id].cnt1 + SegTree[id].cnt0 * 2;
if (l != r)
{
Lazy[id << 1] ^= Lazy[id];
Lazy[id << 1 | 1] ^= Lazy[id];
}
Lazy[id] = 0;
}
void Build(int id, int l, int r)
{
Lazy[id] = 0;
if (l == r)
{
SegTree[id] = Node((Pre[Arr[l]] == 0), (Pre[Arr[r]] == 1), 2 * (Pre[Arr[l]] == 0) + (Pre[Arr[r]] == 1));
return;
}
int mid = (l + r) >> 1;
Build(id << 1, l, mid);
Build(id << 1 | 1, mid + 1, r);
SegTree[id] = SegTree[id << 1] * SegTree[id << 1 | 1];
}
void Update(int id, int l, int r, int i, int j)
{
Fix(id, l, r);
if (j < l || r < i)
{
return;
}
if (i <= l && r <= j)
{
Lazy[id] ^= 1;
Fix(id, l, r);
return;
}
int mid = (l + r) >> 1;
Update(id << 1, l, mid, i, j);
Update(id << 1 | 1, mid + 1, r, i, j);
SegTree[id] = SegTree[id << 1] * SegTree[id << 1 | 1];
}
Node Get(int id, int l, int r, int i, int j)
{
Fix(id, l, r);
if (j < l || r < i)
{
return Node(0, 0, 0);
}
if (i <= l && r <= j)
{
return SegTree[id];
}
int mid = (l + r) >> 1;
return Get(id << 1, l, mid, i, j) * Get(id << 1 | 1, mid + 1, r, i, j);
}
void UpdatePath(int u)
{
while (ChainID[u] != ChainID[root])
{
Update(1, 1, n, Pos[ChainHead[ChainID[u]]], Pos[u]);
u = par[ChainHead[ChainID[u]]];
}
Update(1, 1, n, Pos[root], Pos[u]);
}
bool mark[MaxN];
void Exc()
{
for (int x = 1; x <= n; x++)
{
if ((int)graph[x].size() > 1)
{
root = x;
break;
}
}
PreDFS(root, -1);
CurChain = CurPos = 1;
HLD(root, -1);
Build(1, 1, n);
//cout << Get(1, 1, n, 1, n).sum - Get(1, 1, n, Pos[root], Pos[root]).sum << " ";
for (int x = 1; x <= q; x++)
{
set<int> s;
int d;
cin >> d;
for (int y = 1; y <= d; y++)
{
int u;
cin >> u;
mark[u] ^= 1;
s.insert(u);
}
for (int x : s)
{
if ((int)graph[x].size() == 1)
{
if (mark[x] == 0)
{
UpdatePath(x);
}
}
else
{
if (mark[x] == 1)
{
UpdatePath(x);
}
}
}
int res = 0;
if (Get(1, 1, n, Pos[root], Pos[root]).cnt0)
{
res = Get(1, 1, n, 1, n).sum - Get(1, 1, n, Pos[root], Pos[root]).sum + d;
}
else
{
res = -1;
}
for (int x : s)
{
if ((int)graph[x].size() == 1)
{
if (mark[x] == 0)
{
UpdatePath(x);
}
}
else
{
if (mark[x] == 1)
{
UpdatePath(x);
}
}
mark[x] = 0;
}
cout << res << "\n";
}
}
int main()
{
//freopen("A.INP", "r", stdin);
//freopen("A.OUT", "w", stdout);
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int test = 1;
//cin >> test;
for (int w = 1; w <= test; w++)
{
Inp();
Exc();
}
return 0;
}
