#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ll long long
#define pii pair<int, int>
#define fi first
#define se second
#define rep(i, a, b) for (int i = a; i <= b; ++i)
#define per(i, b, a) for (int i = b; i >= a; --i)
#define pb push_back
#define all(v) (v).begin(), (v).end()
const int MAXN = 5e5 + 10;
const int INF = 1e18 + 5;
const int MOD = 1e9 + 7;
vector<int> g[MAXN];
int a[MAXN], mk[MAXN], dist[MAXN], dep[MAXN], high[MAXN];
int cnt[MAXN], sorted[MAXN];
void dfs(int u, int p = -1, int mx = -1, int opt = 0) {
if (dep[u] + dist[u] > mx) {
mx = dep[u] + dist[u];
opt = u;
}
high[u] = opt;
for (int &v : g[u]) {
if (v==p) continue;
dep[v] = dep[u] + 1;
dfs(v,u,mx,opt);
}
}
void dfs2(int u) {
mk[u] = 1;
for (int &v : g[u]) {
if (mk[v] || dist[u] != dist[v] +1)continue;
dfs2(v);
}
}
int32_t main() {
ios_base::sync_with_stdio(0); cin.tie(nullptr);
int n,k;cin >> n >> k;
rep(i,1,n) dist[i] = INF;
rep(i,1,n-1) {
int u,v;cin >> u >>v;
g[u].pb(v);
g[v].pb(u);
}
queue<pii> bfs;
rep(i,1,k) {
cin >> a[i];
bfs.push({0,a[i]});
}
while (!bfs.empty()) {
auto [cd, u] = bfs.front();
bfs.pop();
if (dist[u] != INF) continue;
dist[u] = cd;
for (int &v : g[u]){
if (dist[v] > cd + 1) bfs.push({cd+1,v});
}
}
dfs(1);
rep(i,1,k) cnt[dep[a[i]] + 1] ++;
rep(i,2,n) cnt[i] += cnt[i-1];
rep(i,1,k) sorted[cnt[dep[a[i]]]++] = a[i];
rep(i,1,k) a[i] = sorted[k-i];
vector<int> ans;
rep(i,1,k) {
if(mk[a[i]]) continue;
ans.pb(high[a[i]]);
dfs2(high[a[i]]);
}
cout << ans.size() << '\n';
for (int &x : ans) cout << x << ' ';
cout << '\n';
return 0;
}
