#include <bits/stdc++.h>
using namespace std;
#define int ll
#define FOR(i,s,e) for(ll i = s; i <= (ll)e; ++i)
#define DEC(i,s,e) for(ll i = s; i >= (ll)e; --i)
#define IAMSPEED ios_base::sync_with_stdio(false); cin.tie(0);
#ifdef LOCAL
#define db(x) cerr << #x << "=" << x << "\n"
#define db2(x, y) cerr << #x << "=" << x << " , " << #y << "=" << y << "\n"
#define db3(a,b,c) cerr<<#a<<"="<<a<<","<<#b<<"="<<b<<","<<#c<<"="<<c<<"\n"
#define dbv(v) cerr << #v << ":"; for (auto ite : v) cerr << ite << ' '; cerr <<"\n"
#define dbvp(v) cerr << #v << ":"; for (auto ite : v) cerr << "{" << ite.f << ',' << ite.s << "} "; cerr << "\n"
#define dba(a,ss,ee) cerr << #a << ":"; FOR(ite,ss,ee) cerr << a[ite] << ' '; cerr << "\n"
#else
#define db(x)
#define db2(x,y)
#define db3(a,b,c)
#define dbv(v)
#define dbvp(v)
#define dba(a,ss,ee)
#endif
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define ll long long
#define pb push_back
#define eb emplace_back
#define all(x) (x).begin(), (x).end()
#define f first
#define s second
#define g0(x) get<0>(x)
#define g1(x) get<1>(x)
#define g2(x) get<2>(x)
#define g3(x) get<3>(x)
#define reach cerr << "LINE: " << __LINE__ << "\n";
typedef pair <ll, ll> pi;
typedef tuple<ll,ll,ll> ti3;
typedef tuple<ll,ll,ll,ll> ti4;
ll rand(ll a, ll b) { return a + rng() % (b-a+1); }
const int MOD = 1e9 + 7;
const int inf = (int)1e9 + 500;
const long long oo = (ll)1e18 + 500;
template <typename T> bool chmax(T& a, const T b) { return a<b ? a = b, 1 : 0; }
template <typename T> bool chmin(T& a, const T b) { return a>b ? a = b, 1 : 0; }
const int MAXN = 500005;
int n,k;
vector<int> V[MAXN];
vector<int> sheeps;
set<int> level[MAXN];
int depth[MAXN];
int twok[MAXN][1];
int st[MAXN], en[MAXN];
int cnt=1;
int rev[MAXN];
void dfs(int x, int p) {
st[x]=cnt;
rev[cnt]=x;
++cnt;
twok[x][0]=p;
for(auto v:V[x])if(v!=p) {
depth[v]=depth[x]+1;
dfs(v,x);
}
en[x]=cnt-1;
}
int dist[MAXN];
set<pi,greater<pi>> s;
vector<int>out;
bool vis[MAXN];
bool is[MAXN];
void clearr(int x) {
if(vis[x])return;
vis[x]=1;
for(auto v:V[x]){
if(vis[v])continue;
if(dist[x]==dist[v]+1)clearr(v);
}
}
int32_t main()
{
IAMSPEED
cin >> n >> k;
FOR(i,1,n-1) {
int a,b; cin >> a >> b;
V[a].pb(b);
V[b].pb(a);
}
FOR(i,1,k) {
int x; cin >> x;
is[x]=1;
sheeps.pb(x);
}
dfs(1,-1);
for(auto i:sheeps) {
s.insert(pi(depth[i],i));
}
queue<int> q;
FOR(i,0,MAXN-1)dist[i]=oo;
for(auto i:sheeps){
q.push(i);
dist[i]=0;
}
while(q.size()) {
int x=q.front();
q.pop();
for(auto v:V[x]){
if(dist[v] > dist[x]+1) {
dist[v]=dist[x]+1;
q.push(v);
}
}
}
for(auto sheep:s){
int x=sheep.s; int dd=sheep.f;
if(vis[x])continue;
int node=x;
while(node != 1 && (dist[twok[node][0]] == depth[x] - depth[twok[node][0]]))node=twok[node][0];
out.pb(node);
clearr(node);
}
cout << out.size() << '\n';
for(auto i:out)cout << i << ' ' ;
}
