#include <bits/stdc++.h>
typedef long long ll;
using namespace std;
vector<int> graph[500001];
int sheep[500001], to_sheep[500001], depth[500001], anc[500001][19];
pair<int, int> highest[500001];
bool guarded[500001];
void dfs(int node = 1, int parent = 0, int d = 0) {
depth[node] = d;
for (int i = 1; i < 19; i++) anc[node][i] = anc[anc[node][i - 1]][i - 1];
int h = node, dist = 1;
for (int i = 18; ~i; i--) if (dist + (1 << i) == to_sheep[anc[h][i]]) {
dist += (1 << i);
h = anc[h][i];
}
highest[node] = {h, dist - 1};
for (int i : graph[node]) if (i != parent) {
anc[i][0] = node;
dfs(i, node, d + 1);
}
}
void guard(int node, int dist_rem, int parent = 0) {
guarded[node] = true;
if (dist_rem) for (int i : graph[node]) if (i != parent) guard(i, dist_rem - 1, node);
}
int main() {
cin.tie(0)->sync_with_stdio(0);
int n, k;
cin >> n >> k;
for (int i = 1; i < n; i++) {
int u, v;
cin >> u >> v;
graph[u].push_back(v);
graph[v].push_back(u);
}
queue<int> q;
for (int i = 1; i <= k; i++) {
cin >> sheep[i];
q.push(sheep[i]);
to_sheep[sheep[i]] = 1;
}
while (q.size()) {
int curr = q.front();
q.pop();
for (int i : graph[curr]) if (!to_sheep[i]) {
to_sheep[i] = to_sheep[curr] + 1;
q.push(i);
}
}
dfs();
vector<int> ans;
sort(sheep + 1, sheep + k + 1, [](int A, int B) { return depth[A] > depth[B]; });
for (int i = 1; i <= k; i++) if (!guarded[sheep[i]]) {
int node, dist;
tie(node, dist) = highest[sheep[i]];
ans.push_back(node);
guard(node, dist);
}
cout << ans.size() << '\n';
for (int i : ans) cout << i << ' ';
return 0;
}
