#include<bits/stdc++.h>
#define fi first
#define se second
#define sz(x) (int)(x).size()
#define pb push_back
#define mkp make_pair
using namespace std;
typedef long long ll;
typedef long double ld;
//#define int long long
const int N = (int)5e5 + 10;
const int inf = 1e9;
vector < int > g[N];
int mnd[N];
int shrt[N], pred[N], h[N];
struct kek{
int ans;
int high;
kek(){
ans = 0;
high = 1e9;
}
};
kek state[N][2];
bool done[N][2];
void dfs(int v, int p, int H){
h[v] = H;
pred[v] = p;
mnd[v] = (shrt[v] == 0 ? 0 : 1e9);
for(auto &u : g[v]){
if(u != p){
dfs(u , v, H + 1);
mnd[v] = min(mnd[v] , mnd[u] + 1);
}
}
}
int did[N][2];
bool bst[N];
bool better(kek &a , kek &b){
if(a.ans == b.ans){
return a.high < b.high;
}
return a.ans < b.ans;
}
void dfs1(int v){
/// mnd[v];
for(auto &u : g[v]){
if(u != pred[v]){
dfs1(u);
if(better(state[u][1] , state[u][0]))
bst[u] = 1;
else
bst[u] = 0;
}
}
vector < int > small;
for(auto &u : g[v]){
if(u == pred[v])
continue;
if(mnd[u] + 1 > mnd[v]){
}else{
small.pb(u);
}
}
for(int fl = 0;fl < 2; ++fl){
for(auto &u : g[v]){
if(u == pred[v])
continue;
if(mnd[u] + 1 > mnd[v]){
state[v][fl].ans += state[u][1].ans;
state[v][fl].high = min(state[v][fl].high, state[u][1].high);
}
}
if(fl == 0){
for(auto &u : small){
state[v][fl].ans += state[u][bst[u]].ans;
state[v][fl].high = min(state[v][fl].high, state[u][bst[u]].high);
}
}else{
/// two options
kek now = state[v][fl];
for(auto &u : small){
now.ans += state[u][1].ans;
now.high = min(now.high, state[u][1].high);
}
/// another option is to cover by the current
for(auto &u : small){
state[v][1].ans += state[u][bst[u]].ans;
state[v][1].high = min(state[v][1].high, state[u][bst[u]].high);
}
int x = h[v] - state[v][fl].high;
bool put = 0;
if(x != mnd[v]){
if(shrt[v] == mnd[v]){
state[v][fl].ans++, put = 1;
state[v][fl].high = min(state[v][fl].high, h[v] - shrt[v]);
}else
state[v][fl].ans = inf;
}
// cerr << " lol " << v << ' ' << now.ans << ' ' << now.high << endl;
if(better(state[v][fl], now)
|| (shrt[v]==0 && (now.high != h[v])) ){
did[v][fl] = 1 + put;
}else{
state[v][fl] = now;
}
}
}
}
bool visited[N][2];
bool ans[N];
void get_ans(int v , int fl){
if(fl == 0){
vector < int > small;
for(auto &u : g[v]){
if(u == pred[v])
continue;
if(mnd[u] + 1 > mnd[v]){
get_ans(u, 1);
}else{
get_ans(u , bst[u]);
}
}
}else{
if(did[v][fl] > 0){
ans[v] = did[v][fl] - 1;
for(auto &u : g[v]){
if(u == pred[v])
continue;
if(mnd[u] + 1 > mnd[v]){
get_ans(u, 1);
}else{
get_ans(u , bst[u]);
}
}
}else{
// assert(shrt[v] != 0);
for(auto &u : g[v]){
if(u == pred[v])
continue;
get_ans(u , 1);
}
}
}
}
signed main(){
ios_base::sync_with_stdio(0), cin.tie(0) , cout.tie(0);
int n , k;
cin >> n >> k;
for(int i = 0; i < n - 1; ++i){
int a , b;
cin >> a >> b;
--a, --b;
g[a].pb(b);
g[b].pb(a);
}
vector < int > o(k);
for(auto &i : o)
cin >> i, --i;
queue < int > bfs;
for(auto &u : o)
bfs.push(u);
fill(shrt , shrt + N , -1);
for(auto &u : o)
shrt[u] = 0;
while(!bfs.empty()){
int v = bfs.front();
bfs.pop();
for(auto &u : g[v]){
if(shrt[u] == -1){
shrt[u] = shrt[v] + 1;
bfs.push(u);
}
}
}
dfs(0 , -1, 0);
dfs1(0);
get_ans(0 , 1);
// cout << "fukk \n";
// for(int i = 0; i < n; ++i){
// if(done[i][0])
// cout << i << ' ' << 0 << ' ' << state[i][0].ans << '\n';
//
// if(done[i][1])
// cout << i << ' ' << 1 << ' ' << state[i][1].ans << '\n';
// cout << " NEW \n";
//
// }
vector < int > take;
for(int i = 0; i < n; ++i){
if(ans[i])
take.pb(i);
}
assert(sz(take) == state[0][1].ans);
cout << state[0][1].ans << endl;
for(auto &u : take)
cout << u + 1 << ' ';
cout << endl;
return 0;
}
