#include <bits/stdc++.h>
// #define int int64_t
const int kMaxN = 5e5 + 5;
int n, k;
int p[kMaxN], dep[kMaxN], dis[kMaxN], id[kMaxN];
bool vis[kMaxN], del[kMaxN];
std::vector<int> G[kMaxN];
void bfs() {
std::queue<int> q;
for (int i = 1; i <= n; ++i)
if (vis[i])
q.emplace(i);
for (; !q.empty();) {
int u = q.front(); q.pop();
for (auto v : G[u]) {
if (!vis[v]) {
dis[v] = dis[u] + 1, vis[v] = 1;
q.emplace(v);
}
}
}
}
void dfs1(int u, int fa) {
p[u] = fa, dep[u] = dep[fa] + 1;
for (auto v : G[u]) {
if (v == fa) continue;
dfs1(v, u);
}
}
void dfs2(int u, int fa) {
del[u] = 1;
for (auto v : G[u]) {
if (v == fa || dis[v] != dis[u] - 1) continue;
dfs2(v, u);
}
}
void dickdreamer() {
std::cin >> n >> k;
for (int i = 1; i < n; ++i) {
int u, v;
std::cin >> u >> v;
G[u].emplace_back(v), G[v].emplace_back(u);
}
for (int i = 1; i <= k; ++i) {
std::cin >> id[i];
vis[id[i]] = 1;
}
bfs(), dfs1(1, 0);
std::sort(id + 1, id + 1 + n, [&] (int i, int j) { return dep[i] > dep[j]; });
std::vector<int> vec;
for (int c = 1; c <= k; ++c) {
int i = id[c];
if (del[i]) continue;
for (; p[i] && dis[p[i]] == dis[i] + 1; i = p[i]) {}
dfs2(i, 0);
vec.emplace_back(i);
}
std::cout << vec.size() << '\n';
for (auto x : vec) std::cout << x << ' ';
}
int32_t main() {
std::ios::sync_with_stdio(0), std::cin.tie(0), std::cout.tie(0);
int T = 1;
// std::cin >> T;
while (T--) dickdreamer();
// std::cerr << 1.0 * clock() / CLOCKS_PER_SEC << "s\n";
return 0;
}
