#include<bits/stdc++.h>
using namespace std;
#define int long long
#define fi first
#define se second
#define pii pair<int,int>
#define inp(name) freopen(name, "r", stdin);
#define out(name) freopen(name, "w", stdout);
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int rnd(int l, int r){ return (l + (rng() % (r - l + 1))); }
const int N = 5e5 + 5;
const int mod = 998244353;
int n, k;
int a[N], depth[N], d[N], ans[N], check[N];
vector <int> adj[N];
bool cmp(int a, int b){
return depth[a] > depth[b];
}
void bfs(){
queue <int> q;
fill (d + 1, d + n + 1, 1e9);
for (int i = 1; i <= k; i ++){
d[a[i]] = 0; q.push(a[i]);
}
while (!q.empty()){
int u = q.front(); q.pop();
for (auto i : adj[u]){
if (d[i] == 1e9){
d[i] = d[u] + 1; q.push(i);
}
}
}
}
void pre_dfs(int u, int v){
for (auto i : adj[u]){
if (i == v) continue;
depth[i] = depth[u] + 1;
pre_dfs(i, u);
}
}
void dfs(int u, int v, int res, int node){
if (res < depth[u] + d[u]){
res = depth[u] + d[u]; node = u;
}
ans[u] = node;
for (auto i : adj[u]){
if (i == v) continue;
dfs(i, u, res, node);
}
}
void update(int u){
check[u] = 1;
for (auto i : adj[u]){
if (check[i] || d[i] + 1 != d[u]) continue;
update(i);
}
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> k;
for (int i = 1; i < n; i ++){
int u, v; cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
for (int i = 1; i <= k; i ++){
cin >> a[i];
}
bfs();
pre_dfs(1, 0);
dfs(1, 0, 0, 1);
sort(a + 1, a + k + 1, cmp);
vector <int> trace;
for (int i = 1; i <= k; i ++){
if (check[a[i]]) continue;
trace.push_back(ans[a[i]]);
update(ans[a[i]]);
}
cout << trace.size() << '\n';
for (auto i : trace) cout << i << " ";
}
