#include "bits/stdc++.h"
using namespace std;
typedef pair<int, int> pii;
#define f first
#define s second
const int N=5e5+1;
int n, k;
vector<int> adj[N];
bool mark[N];
int dp[N], d[N];
vector<int> ans;
void dfs(int x, int par){
dp[x]=-1;
if(!d[x]) mark[x]=1;
for(int k:adj[x]){
if(k==par) continue;
dfs(k, x);
if(mark[k]) mark[x]=1;
dp[x]=max(dp[x], dp[k]-1);
}
if(mark[x] && dp[x]==d[x]) mark[x]=0;
if(mark[x] && d[par]!=d[x]+1){
ans.push_back(x);
dp[x]=d[x];
mark[x]=0;
}
}
int main(){
cin.tie(0)->sync_with_stdio(0);
cin >> n >> k;
for(int i=0; i<n-1; i++){
int u,v; cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
for(int i=1; i<=n; i++){
d[i]=-1;
}
queue<int> q;
while(k--){
int sheep;
cin >> sheep;
d[sheep]=0;
q.push(sheep);
}
for(; q.size(); q.pop()){
int x=q.front();
// cout << "d[" << x << "] " << d[x] << "\n";
for(int k:adj[x]){
if(d[k]==-1) d[k]=d[x]+1, q.push(k);
}
}
dfs(1, 0);
cout << ans.size() << "\n";
for(int x:ans) cout << x << " ";
}
// does it ever get lonely thinking you could live without me?
