#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define fi first
#define se second
const int N = 5e5 + 5;
int n, k;
vector<int> adj[N];
vector<int> G[N];
int sheep[N];
int h[N], par[N][20];
int dist[N], vis[N];
multiset<pair<int, int> > ms;
vector<int> ans;
void dfs(int u, int p) {
for (int v : adj[u]) {
if (v != p) {
h[v] = h[u] + 1;
par[v][0] = u;
dfs(v, u);
}
}
}
int main() {
ios_base::sync_with_stdio(0); cin.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++) {
int x; cin >> x;
sheep[x] = 1;
}
for (int i = 1; i <= n; i++) {
for (int j = 0; j <= 18; j++) {
par[i][j] = -1;
}
}
h[1] = 1; dfs(1, 1);
for (int j = 1; j <= 18; j++) {
for (int i = 1; i <= n; i++) {
if (par[i][j - 1] != -1) {
par[i][j] = par[par[i][j - 1]][j - 1];
}
}
}
queue<int> q;
for (int i = 1; i <= n; i++) {
if (sheep[i] == 1) {
q.push(i);
} else {
dist[i] = 1e9;
}
}
while (!q.empty()) {
int u = q.front();
q.pop();
for (int v : adj[u]) {
if (dist[v] == 1e9) {
dist[v] = dist[u] + 1;
q.push(v);
}
}
}
for (int i = 1; i <= n; i++) {
if (sheep[i] == 1) ms.insert({-h[i], i});
for (int v : adj[i]) {
if (dist[i] == dist[v] + 1) G[i].push_back(v);
}
}
while (!ms.empty()) {
int pre = ms.begin() -> se;
int cur = pre;
for (int i = 18; i >= 0; i--) {
if (par[cur][i] != -1 && dist[par[cur][i]] == h[pre] - h[par[cur][i]]) {
cur = par[cur][i];
}
}
vector<int> take;
q.push(cur); vis[cur] = 1;
while (!q.empty()) {
int u = q.front();
q.pop();
if (dist[u] == 0) take.push_back(u);
for (int v : G[u]) {
if (vis[v] == 0) {
vis[v] = 1;
q.push(v);
}
}
}
for (int i : take) ms.erase(ms.find({-h[i], i}));
ans.push_back(cur);
}
cout << (int)ans.size() << "\n";
for (int i : ans) cout << i << " ";
}
