#include <bits/stdc++.h>
#define int long long
using namespace std;
int a,b;
vector <int> z[1000005];
vector <int> v;
int high[1000005];
int par[500005][25];
bool cmp(int a,int b){
return high[a]>high[b];
}
void dfs(int i,int parent){
for (auto p:z[i]){
if (p==parent){
continue;
}
high[p]=high[i]+1;
par[p][0]=i;
dfs(p,i);
}
}
bool vis[1000005];
int cnt[1000005];
void bfs1(){
queue<int> q;
for (auto p:v){
q.push(p);
vis[p]=true;
cnt[p]=0;
}
while (q.size()){
int pos=q.front();
q.pop();
for (auto p:z[pos]){
if (vis[p]){
continue;
}
vis[p]=true;
cnt[p]=cnt[pos]+1;
q.push(p);
}
}
}
vector <int> res;
int jump(int x){
for (int i=20;i>=0;i--){
int nxt=par[x][i];
if (cnt[nxt]==high[x]-high[nxt]){
x=par[x][i];
}
}
return x;
}
void bfs(int sta,int len){
queue<pair<int,int>> q;
q.push({sta,len});
vis[sta]=true;
while (q.size()){
auto [pos,remain]=q.front();
q.pop();
if (remain==0){
continue;
}
for (auto p:z[pos]){
if (vis[p]){
continue;
}
vis[p]=true;
q.push({p,remain-1});
}
}
}
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> a >> b;
for (int i=1;i<a;i++){
int x,y;
cin >> x >> y;
z[x].push_back(y);
z[y].push_back(x);
}
for (int i=1;i<=b;i++){
int x;
cin >> x;
v.push_back(x);
}
high[0]=-1;
par[1][0]=1;
dfs(1,1);
for (int j=1;j<=20;j++){
for (int i=1;i<=a;i++){
par[i][j]=par[par[i][j-1]][j-1];
}
}
sort(v.begin(),v.end(),cmp);
bfs1();
memset(vis,false,sizeof vis);
for (auto p:v){
if (vis[p]){
continue;
}
int nxt=jump(p);
int len=high[p]-high[nxt];
res.push_back(nxt);
bfs(nxt,len);
}
cout << res.size() << "\n";
for (auto p:res){
cout << p << " ";
}
return 0;
}
