// PhuThuyRuntime <3
// A secret makes a woman woman
#include <bits/stdc++.h>
using namespace std;
#define eb emplace_back
#define ef emplace_front
#define pb push_back
#define pf push_front
#define all(v) v.begin(), v.end()
#define ins insert
#define lb lower_bound
#define ub upper_bound
#define fo(i, l, r) for(int i = l; i <= r; i++)
#define foi(i, l, r) for(int i = l; i >= r; i--)
#define elif else if
#define el cout << "\n";
#define pii pair<int, int>
#define pli pair<ll, int>
#define pll pair<ll, ll>
#define pil pair<int, ll>
#define fi first
#define se second
#define in(x) freopen(x, "r", stdin)
#define out(x) freopen(x, "w", stdout)
#define ll long long
#define ull unsigned long long
#define pob pop_back
#define bs binary_search
#define vi vector<int>
#define vii vector<pair<int, int>>
#define getbit(i, j) ((i >> j) & 1)
#define offbit(i, j) ((1 << j) ^ i)
#define onbit(i, j) ((1 << j) | i)
const int N = 1e5 + 2;
const ll mod = 1e9 + 7;
const int inf = INT_MAX;
const int base = 31;
const long double EPS = 1e-9;
const long double pi = acos(-1.0);
int n, k, c[5 * N];
vi adj[5 * N];
void inp(){
cin >> n >> k;
fo(i, 1, n - 1){
int u, v; cin >> u >> v;
adj[u].eb(v);
adj[v].eb(u);
}
fo(i, 1, k) cin >> c[i];
}
bool visited[5 * N];
int dis[5 * N];
void bfs() {
queue<int> Q;
fo(i, 1, k){
visited[c[i]] = true;
Q.push(c[i]);
}
while (Q.size() > 0) {
int u = Q.front(); Q.pop();
for (auto v: adj[u]) {
if (visited[v]) continue;
visited[v] = true;
dis[v] = dis[u] + 1;
Q.push(v);
}
}
}
int dep[5 * N], up[5 * N][20];
void dfs(int u, int fa){
for(auto v : adj[u]){
if(v == fa) continue;
dep[v] = dep[u] + 1;
dfs(v, u);
up[v][0] = u;
}
}
bool cmp(int a, int b){
return dep[a] > dep[b];
}
bool done[5 * N];
void mark(int u){
done[u] = 1;
for(auto v : adj[u]){
if(done[v]) continue;
if(dis[v] + 1 != dis[u]) continue;
mark(v);
}
}
void sol(){
dfs(1, 0);
bfs();
fo(j, 1, 19){
fo(i, 1, n) up[i][j] = up[up[i][j - 1]][j - 1];
}
sort(c + 1, c + k + 1, cmp);
vi ans;
fo(i, 1, k){
int u = c[i];
if(done[u]) continue;
int x = u;
foi(j, 19, 0){
int v = up[x][j];
if(v != 0 && dep[u] - dep[v] == dis[v]) x = v;
}
mark(x);
ans.eb(x);
}
sort(ans.begin(), ans.end());
cout << ans.size() << '\n';
for (auto v: ans) if(v == ans.back()) cout << v; else cout << v << ' ';
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
inp();
sol();
return 0;
}
