#include <bits/stdc++.h>
using namespace std;
template<typename T>
void out(T x) { cout << x << endl; exit(0); }
#define watch(x) cout << (#x) << " is " << (x) << endl
using ll = long long;
const int maxn = 1e6 + 5;
int n,k;
vector<int> g[maxn];
vector<int> a;
int par[maxn];
int dep[maxn];
void dfs(int at, int p) {
for (int to: g[at]) {
if (to == p) continue;
par[to]=at;
dep[to]=1+dep[at];
dfs(to,at);
}
}
int rad[maxn];
void gen_rad() {
for (int i=1; i<=n; i++) {
rad[i]=-1;
}
queue<int> qq;
for (int x: a) {
rad[x]=0;
qq.push(x);
}
while (qq.size()) {
int at = qq.front();
qq.pop();
for (int to: g[at]) {
if (rad[to]==-1) {
rad[to]=1+rad[at];
qq.push(to);
}
}
}
}
bool done[maxn];
void mark_done(int x) {
queue<int> qq;
qq.push(x);
while (qq.size()) {
int at = qq.front();
qq.pop();
done[at] = true;
for (int to: g[at]) {
if (done[to]) continue;
if (rad[to] == rad[at]-1) {
qq.push(to);
}
}
}
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin>>n>>k;
for (int i=0; i<n-1; i++) {
int u,v; cin>>u>>v;
g[u].push_back(v);
g[v].push_back(u);
}
a.resize(k);
for (int i=0; i<k; i++) {
cin>>a[i];
}
dfs(1,0);
gen_rad();
sort(a.begin(), a.end(), [&](int x, int y) {
return dep[x]<dep[y];
});
reverse(a.begin(),a.end());
vector<int> ans;
for (int x: a) {
if (done[x]) continue;
int at = x;
while (rad[par[at]] == 1+rad[at]) {
at = par[at];
}
ans.push_back(at);
mark_done(at);
}
cout<<ans.size()<<"\n";
sort(ans.begin(),ans.end());
for (int x: ans) cout<<x<<" ";
cout<<endl;
return 0;
}
