#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif
const int N = 5e5 + 5;
int n, k;
int d[N], s[N], pr[N], dep[N];
bool del[N];
vector<int> g[N];
void dfs(int u) {
for (int v : g[u]) {
if (v != pr[u]) {
dep[v] = dep[u] + 1;
pr[v] = u;
dfs(v);
}
}
}
void DFS(int u) {
del[u] = 1;
for (int v : g[u]) {
if (!del[v] && d[v] + 1 == d[u]) {
DFS(v);
}
}
}
void bfs() {
memset(d, -1, sizeof(d));
queue<int> q;
for (int i = 1; i <= k; ++i) {
d[s[i]] = 0;
q.push(s[i]);
}
while (q.size()) {
int u = q.front(); q.pop();
for (int v : g[u]) {
if (d[v] == -1) {
d[v] = d[u] + 1;
q.push(v);
}
}
}
}
int main() {
ios::sync_with_stdio(false); cin.tie(nullptr);
cin >> n >> k;
for (int i = 1; i < n; ++i) {
int u, v; cin >> u >> v;
g[u].push_back(v);
g[v].push_back(u);
}
for (int i = 1; i <= k; ++i) {
cin >> s[i];
}
bfs();
dfs(1);
sort(s + 1, s + k + 1, [&](int i, int j) {
return dep[i] > dep[j];
});
vector<int> res;
for (int i = 1; i <= k; ++i) {
if (del[s[i]]) {
continue;
}
int u = s[i], p = u;
while (d[pr[p]] == dep[u] - dep[pr[p]]) {
p = pr[p];
}
DFS(p);
res.push_back(p);
}
cout << res.size() << "\n";
for (int x : res) {
cout << x << " ";
}
return 0;
}
