#include <iostream>
#include <string>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <map>
#include <iterator>
#include <set>
#include <random>
#include <unordered_map>
#include <queue>
#include <cassert>
#include <stack>
#include <numeric>
#include <deque>
using namespace std;
typedef long long ll;
typedef long double ld;
const ll md1 = 1'000'000'000;
const ll md2 = 998244353;
const ll mdd = 666013;
int n, k;
const int N = 500'001;
vector<int> g[N];
bool sh[N];
void dfs(int nw, vector<bool>& alive, vector<int>& dis, queue<int>& q, vector<int>& st, vector<bool>& sp) {
alive[nw] = false;
q.push(nw);
sh[nw] = false;
for (int w : g[nw]) {
if (alive[w]) {
if (dis[w] < dis[nw])
dfs(w, alive, dis, q, st, sp);
}
}
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;
//cin >> t;
while (t--) {
cin >> n >> k;
vector<pair<int, int>> e(n - 1);
for (int i = 1; i < n; i++) {
int v, u;
cin >> v >> u;
v--, u--;
e[i - 1] = { v, u };
g[v].push_back(u);
g[u].push_back(v);
}
for (int i = 0; i < k; i++) {
int v;
cin >> v;
sh[v - 1] = true;
}
vector<int> st(n);
queue<int> q;
vector<bool> alive(n, true);
for (int i = 0; i < n; i++) {
st[i] = g[i].size();
if (st[i] == 1 && !sh[i]) {
q.push(i);
alive[i] = false;
}
}
while (!q.empty()) {
int nw = q.front();
q.pop();
for (int w : g[nw]) {
st[w]--;
if (alive[w] && !sh[w] && st[w] == 1) {
q.push(w);
alive[w] = false;
}
}
}
vector<int> dis(n, -1);
for (int i = 0; i < n; i++) {
if (sh[i]) {
q.push(i);
dis[i] = 0;
}
}
while (!q.empty()) {
int nw = q.front();
q.pop();
for (int w : g[nw]) {
if (alive[w] && dis[w] == -1) {
dis[w] = dis[nw] + 1;
q.push(w);
}
}
}
vector<bool> sp(n, true);
for (int i = 0; i < n; i++)
for (int w : g[i])
if (alive[w] && dis[w] > dis[i])
sp[i] = false;
for (int i = 0; i < n; i++)
if (st[i] <= 1 && alive[i]) {
q.push(i);
alive[i] = false;
}
int ans = 0;
vector<int> res;
while (!q.empty()) {
int nw = q.front();
q.pop();
if (sp[nw]) {
ans++;
res.push_back(nw);
dfs(nw, alive, dis, q, st, sp);
}
else {
if (sh[nw]) {
for (int w : g[nw]) {
st[w]--;
sh[w] = true;
if (alive[w] && (st[w] <= 1 || sp[w])) {
q.push(w);
alive[w] = false;
}
}
}
else {
for (int w : g[nw]) {
st[w]--;
if (alive[w] && st[w] <= 1 && !(sp[w] && !sh[w])) {
q.push(w);
alive[w] = false;
}
}
}
}
}
cout << ans << "\n";
sort(res.begin(), res.end());
for (int w : res)
cout << w + 1 << " ";
cout << "\n";
}
return 0;
}
