This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
//#pragma GCC optimize("Ofast,unroll-loops")
#include <bits/stdc++.h>
using namespace std;
typedef long long llo;
#define mp make_pair
#define pb push_back
#define a first
#define b second
//#define endl '\n'
int n,k;
vector<int> adj[500001];
vector<int> ans;
int lev[500001];
int par[500001][20];
int vis[500001];
int vis2[500001];
int mi[500001];
void dfs(int no,int par2=-1,int levv=0){
lev[no]=levv;
par[no][0]=par2;
for(auto j:adj[no]){
if(j!=par2){
dfs(j,no,levv+1);
}
}
}
//int cot=-1;
//int dist[2001][2001];
/*void dfs2(int no,int par2=-1,int levv=0){
dist[cot][no]=levv;
for(auto j:adj[no]){
if(j!=par2){
dfs2(j,no,levv+1);
}
}
}*/
void dfs3(int no){
vis[no]=1;
for(auto j:adj[no]){
if(mi[j]==mi[no]-1 and vis[j]==0){
dfs3(j);
}
}
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin>>n>>k;
for(int i=0;i<n-1;i++){
int aa,bb;
cin>>aa>>bb;
aa--;
bb--;
adj[aa].pb(bb);
adj[bb].pb(aa);
}
vector<int> ss(k);
for(int i=0;i<k;i++){
cin>>ss[i];
ss[i]--;
vis2[ss[i]]=1;
}
for(int i=0;i<n;i++){
mi[i]=n;
}
queue<pair<int,int>> mm;
for(auto j:ss){
mi[j]=0;
mm.push({0,j});
}
while(mm.size()){
pair<int,int> no=mm.front();
mm.pop();
for(auto j:adj[no.b]){
if(mi[j]==n){
mi[j]=no.a+1;
mm.push({mi[j],j});
}
}
}
/*for(int i=0;i<n;i++){
cot=i;
dfs2(i);
}*/
dfs(0);
for(int j=1;j<20;j++){
for(int i=0;i<n;i++){
if(par[i][j-1]==-1){
par[i][j]=-1;
}
else{
par[i][j]=par[par[i][j-1]][j-1];
}
}
}
vector<pair<int,int>> tt;
for(auto j:ss){
tt.pb({lev[j],j});
}
sort(tt.begin(),tt.end());
/*for(int i=0;i<n;i++){
cout<<par[i][0]<<",";
}
cout<<endl;
for(int i=0;i<n;i++){
cout<<par[i][1]<<",";
}
cout<<endl;
cout<<par[19][0]<<",,"<<par[19][1]<<endl;*/
while(tt.size()){
if(vis[tt.back().b]){
tt.pop_back();
continue;
}
int x=tt.back().b;
int cur=x;
int co=0;
for(int j=19;j>=0;j--){
if(par[cur][j]==-1){
continue;
}
if(co+(1<<j)==mi[par[cur][j]]){
cur=par[cur][j];
co+=(1<<j);
}
}
// cout<<par[19][1]<<endl;
// cout<<x<<":"<<cur<<":"<<co<<endl;
/*int pp=x;
int cur=par[x][0];
int co=1;
while(cur!=-1){
if(co==mi[cur]){
pp=cur;
cur=par[cur][0];
co++;
continue;
}
cur=par[cur][0];
co++;
}
cur=pp;*/
dfs3(cur);
/*for(int i=0;i<k;i++){
if(dist[cur][ss[i]]==mi[cur]){
vis[ss[i]]=1;
}
}*/
ans.pb(cur);
tt.pop_back();
}
cout<<ans.size()<<endl;
for(auto j:ans){
cout<<j+1<<" ";
}
cout<<endl;
return 0;
}
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