#include<bits/stdc++.h>
#define PB push_back
#define maxn 500007
#define bit(x,i) ((x>>i)&1)
#define S second
#define F first
#define MP make_pair
#define epsilon 0.000001
using namespace std;
typedef pair<int,int> pii;
typedef pair<double,double> pdd;
const int inf = 1e18;
const int mod = 1e9+7;
const double PI = acos(-1);
int n,k,dis[maxn],s[maxn],dep[maxn],h[maxn],bio[maxn];
vector<int> adj[maxn];
void readData(){
cin>>n>>k;
for (int i=1;i<n;i++){
int u,v;
cin>>u>>v;
adj[u].PB(v);
adj[v].PB(u);
}
for (int i=1;i<=k;i++) cin>>s[i];
}
void dfs_init(int x, int p, int mx, int opt){
int sum=dep[x]+dis[x];
if (sum>mx){
mx=sum;
opt=x;
}
h[x]=opt;
for (auto v:adj[x]){
if (v==p) continue;
dep[v]=dep[x]+1;
dfs_init(v,x,mx,opt);
}
}
void bfs(){
memset(dis,-1,sizeof(dis));
queue<int> q;
for (int i=1;i<=k;i++){
dis[s[i]]=0;
q.push(s[i]);
}
while (q.size()){
int u=q.front();
q.pop();
for (auto v:adj[u]){
if (dis[v]!=-1) continue;
dis[v]=dis[u]+1;
q.push(v);
}
}
}
bool cmp(int x, int y){
return dep[x]>dep[y];
}
void dfs_cover(int x){
bio[x]=1;
for (auto v:adj[x])
if (!bio[v]&&dis[x]==dis[v]+1) dfs_cover(v);
}
void solve(){
bfs();
dfs_init(1,0,-1,0);
sort(s+1,s+k+1,cmp);
vector<int> ans;
for (int i=1;i<=k;i++){
if (bio[s[i]]) continue;
ans.PB(h[s[i]]);
dfs_cover(h[s[i]]);
}
cout<<ans.size()<<"\n";
for (auto x:ans) cout<<x<<" ";
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
//freopen("SHEEP.inp","r",stdin);
//freopen(".out","w",stdout);
readData();
solve();
return 0;
}
/*
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=====`-.____`.___ \_____/___.-`___.-'=====
`=---='
*/
