include<bits/stdc++.h>

using namespace std;

define endl "\n"

define pb push_back

define ll long long

const int maxn=1e6+1;

vector<int>adj[maxn],queries[maxn];
int n,q,par[maxn],rnk[maxn],ancestor[maxn];
bool visited[maxn];
map<pair\<int,int>,int>mp;
vector<pair\<int,int>>ans;

int find_set(int u){
while(par[u]!=u)u=par[u];
return u;
}

void union_set(int x,int y){
int xroot=find_set(x);
int yroot=find_set(y);
if(xroot==yroot)return;
if(rnk[xroot]<rnk[yroot])par[xroot]=yroot; else if(rnk[xroot]>rnk[yroot])par[yroot] = xroot;
else{
par[xroot]=yroot;
rnk[yroot]++;
}
}

void dfs(int w){
visited[w]=true;
ancestor[w]=w;
for(int u:adj[w]){
if(!visited[u]){
dfs(u);
union_set(w,u);
ancestor[find_set(u)] = w;
}
}
for(int u:queries[w]){
if(visited[u]){
mp[{min(w,u),max(u,w)}]=ancestor[find_set(u)];
}
}
}

int main() {
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin>>n>>q;
for(int i = 1; i < n; i++) {
int u, v;
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
for(int i = 1; i <= n; i++)
par[i] = i;
for (int i=1;i<=q;i++) {
int u, v;
cin >> u >> v;if (u>v)swap(u,v);ans.pb({u,v});
queries[u].push_back(v);
queries[v].push_back(u);
}
dfs(1);
for (auto u:ans)cout<<mp[u]<<endl;
}

Bo nè hihi

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