#include <bits/stdc++.h>
using namespace std;
#define sp " "
#define endl "\n"
#define fileio() freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout)
#define fastio() cin.tie(0), ios_base::sync_with_stdio(0)
#define pb push_back
#define pii pair<int, int>
#define st first
#define nd second
#define N 500005
const int modulo = 1e9 + 7;
int flag[N], dep[N], maks[N], up[N], mark[N];
vector<int> child[N], adj[N];
void dfs(int node, int root, int d){
dep[node] = d;
for (auto i : adj[node]){
if (i == root) continue;
child[node].pb(i);
dfs(i, node, d + 1);
}
}
void dfs2(int node){
maks[node] = modulo;
if (mark[node]) maks[node] = 0;
for (auto i : child[node])
{
dfs2(i);
maks[node] = min(maks[node], maks[i] + 1);
}
//cout<<node<<sp<<maks[node]<<endl;
}
void dfs3(int node, int val){
vector<int> pre, suf;
up[node] = val;
//cout<<"! "<<node<<sp<<val<<endl;
if (mark[node]) val = 0;
pre.pb(modulo);
for (int i = 0; i < (int)child[node].size() - 1; i++)
{
pre.pb(min(maks[child[node][i]], pre.back()));
}
suf.pb(modulo);
for (int i = (int)child[node].size() - 1; i > 0; i--)
{
suf.pb(min(maks[child[node][i]], suf.back()));
}
reverse(suf.begin(), suf.end());
for (int i = 0; i < child[node].size(); i++)
dfs3(child[node][i], min(val, min(pre[i], suf[i]) + 1) + 1);
}
pii dfs4(int node){
int curr = modulo, dist = 0;
for (auto i : child[node])
{
pii tmp = dfs4(i);
curr = min(curr, tmp.st + 1);
dist = max(dist, tmp.nd);
}
if (dist == 0 && mark[node]) curr = 0;
if (dist > curr) curr = modulo;
//cout<<node<<sp<<dist<<sp<<curr<<sp<<up[node]<<endl;
dist--;
if (curr != modulo && (abs(up[node] - curr) <= 1 || node == 1))
{
flag[node] = 1;
dist = curr;
curr = modulo;
}
return make_pair(curr, dist);
}
int32_t main(){
//fileio();
fastio();
int n, k;
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++){
int tmp;
cin>>tmp;
mark[tmp] = 1;
}
dfs(1, 0, 1);
dfs2(1);
dfs3(1, modulo);
pii tmp = dfs4(1);
vector<int> v;
for (int i = 1; i <= n; i++)
if (flag[i]) v.pb(i);
sort(v.begin(), v.end());
cout<<v.size()<<endl;
for (auto i : v)
cout<<i<<sp;
cout<<endl;
//cerr<<"time taken : "<<(float)clock() / CLOCKS_PER_SEC<<" seconds\n";
}
