#include <bits/stdc++.h>
#define noSuccess t--
#define int long long
#define pb push_back 
#define F first	
#define S second
#define YouCanDoGreatThings ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define all(s) s.begin(),s.end()
#define yes "YES\n"
#define no "NO\n"
#define sz size
 
using namespace std;
const int maxn = 1e6;
vector<int>g[maxn];
int used[maxn];
int timer;
void dfs(int v){
  used[v]=timer;
  for(auto& to: g[v]){
    if(used[to]==1e10) dfs(to);
  }
}
void tryAgain(){
  int n,m;
  cin>>n>>m;
  for(int i=1;i<=n-1;i++){
    int u,v;
    cin>>u>>v;
    g[u].pb(v);
    g[v].pb(u);
  }
  int a[m+5],b[m+5];
  for(int i=1;i<=m;i++){
    cin>>a[i]>>b[i];
  }
  set<int>st;
  int ans=INT_MAX,pos=0;
  for(int ms=1;ms<(1<<n);ms++){
    int cal=0;
    for(int i=1;i<=n;i++){
      used[i]=1e10;
      int k=i-1;
      if((1<<k) & ms){
        used[i]=-1;
        cal++;
      }
    }
    timer=0;
    for(int i=1;i<=n;i++){
      if(used[i]==1e10){
        ++timer;
        dfs(i);
      }
    }
    bool ok=1;
    for(int i=1;i<=m;i++){
      if(used[b[i]]==-1 || used[a[i]]==-1) continue;
      if(used[a[i]]==used[b[i]]){
        ok=0;
        break;
      }
    }
    if(ans>=cal && ok==1){
      ans=cal;
      pos=ms;
    }
  }
  for(int i=1;i<=n;i++){
    int k=i-1;
    used[i]=1e10;
    if((1<<k) & pos){
      used[i]=-1;
      st.insert(i);
    }
  }
  timer=0;
  for(int i=1;i<=n;i++){
    if(used[i]==1e10 && used[i]!=-1){
      ++timer;
      dfs(i);
    }
  }
  for(int i=1;i<=n;i++){
    int ok=0;
    for(int j=1;j<=m;j++){
      if(a[i]==i && a[j]==i) {
        ok=1;
        break;
      }
    }
    if(ok==1) continue;
    for(auto to : g[i]){
      if(used[to]!=-1) ok=1;
    }
    if(ok==1) st.erase(i);
  }
  // for(int i=1;i<=n;i++) cout<<used[i]<<' ';
  cout<<st.sz()<<'\n';
  for(auto to : st){
    cout<<to<<' ';
  }
}
signed main(){
  YouCanDoGreatThings
  // freopen("length.in", "r", stdin);
  // freopen("length.out", "w", stdout);
  int t = 1;
  // cin >> t;
  while(noSuccess){
    tryAgain();
  }
}