#include <bits/stdc++.h>
using namespace std;
#define TRACE(x) cerr << #x << " = " << x << endl
#define _ << " _ " <<
#define fi first
#define se second
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef vector<int> vi;
const int MAXN = 1e6 + 10;
int n, k;
vi e[MAXN], sheep;
int r[MAXN];
int p[MAXN], depth[MAXN];
vi sol;
bool vis[MAXN];
void input() {
cin >> n >> k;
for (int i = 0; i < n - 1; i++) {
int x, y;
cin >> x >> y;
e[x].push_back(y);
e[y].push_back(x);
}
sheep.resize(k);
for (int i = 0; i < k; i++) cin >> sheep[i];
}
void calc_radiuses() {
fill(r + 1, r + n + 1, -1);
queue<int> Q;
for (auto x : sheep) {
r[x] = 0;
Q.push(x);
}
while (!Q.empty()) {
int x = Q.front();
Q.pop();
for (auto y : e[x]) {
if (r[y] == -1) {
r[y] = r[x] + 1;
Q.push(y);
}
}
}
}
void calc_depths() {
int root = rand() % n + 1;
p[root] = -1;
depth[root] = 0;
queue<int> Q;
Q.push(root);
while (!Q.empty()) {
int x = Q.front();
Q.pop();
for (auto y : e[x]) {
if (y == p[x]) continue;
p[y] = x;
depth[y] = depth[x] + 1;
Q.push(y);
}
}
}
void visit(int x) {
queue<int> Q;
Q.push(x);
while (!Q.empty()) {
int y = Q.front();
Q.pop();
vis[y] = true;
for (auto z : e[y]) {
if (r[z] == r[y] - 1 && !vis[z]) Q.push(z);
}
}
}
void solve() {
vector<vi> buckets(n);
for (auto x : sheep) buckets[depth[x]].push_back(x);
sheep.clear();
for (auto& b : buckets) sheep.insert(sheep.end(), b.begin(), b.end());
reverse(sheep.begin(), sheep.end());
for (auto x : sheep) {
if (vis[x]) continue;
int y = x;
while (p[y] != -1 && r[p[y]] == r[y] + 1) y = p[y];
sol.push_back(y);
visit(y);
}
}
void output() {
cout << sol.size() << '\n';
for (auto it : sol) cout << it << ' ';
cout << '\n';
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
srand(time(0));
input();
calc_radiuses();
calc_depths();
solve();
output();
return 0;
}
