#include<iostream>
#include<vector>
#include<algorithm>
#include<queue>
using namespace std;
const int MAX_N=5e5+4;
int n;
vector<int>g[MAX_N];
bool sheep[MAX_N];
int dist[MAX_N];
int highest[MAX_N];
int depth[MAX_N];
int dp[MAX_N][2];
int minreach[MAX_N][2];
bool place[MAX_N];
bool all[MAX_N];
vector<int>guys;
void dfs(int u,int par)
{
for(int v:g[u])
{
if(v==par)continue;
dfs(v,u);
}
if(sheep[u])
{
int both_dp=0,both_minreach=1e9;
minreach[u][0]=1e9;minreach[u][1]=1e9;
for(int v:g[u])
{
if(v==par)continue;
both_dp+=dp[v][0];
both_minreach=min(both_minreach,minreach[v][0]);
}
dp[u][1]=both_dp;minreach[u][1]=both_minreach;
if(both_minreach>depth[u])
{
minreach[u][0]=depth[u];
dp[u][0]=both_dp+1;
place[u]=1;
}
else
{
minreach[u][0]=both_minreach;
dp[u][0]=both_dp;
}
}
else
{
int both_dp=0,dp_without=0,dp_with=0;
int both_minreach=1e9,reach_without=1e9,reach_with=1e9;
minreach[u][0]=1e9;minreach[u][1]=1e9;
int mosthigh=highest[u];
for(int v:g[u])
{
if(v==par)continue;
if(highest[v]==mosthigh)
{
dp_without+=dp[v][1];
dp_with+=dp[v][0];
reach_with=min(reach_with,minreach[v][0]);
reach_without=min(reach_without,minreach[v][1]);
}
else
{
both_dp+=dp[v][0];
both_minreach=min(both_minreach,minreach[v][0]);
}
}
dp[u][1]=both_dp+dp_without;
minreach[u][1]=min(both_minreach,reach_without);
if(both_minreach<=2*depth[u]-mosthigh)
{
dp[u][0]=dp[u][1];
minreach[u][0]=minreach[u][1];
}
else
{
if(dp_with==dp_without or dist[u]+depth[u]<mosthigh)
{
dp[u][0]=both_dp+dp_with;
minreach[u][0]=min(both_minreach,reach_with);
all[u]=1;
}
else
{
dp[u][0]=both_dp+dp_without+1;
minreach[u][0]=min(both_minreach,reach_without);
minreach[u][0]=min(minreach[u][0],depth[u]-dist[u]);
place[u]=1;
}
}
}
}
void backdfs(int u,int par,bool state)
{
if(state==0 && place[u])guys.push_back(u);
if(sheep[u])
{
for(int v:g[u])
{
if(v==par)continue;
backdfs(v,u,0);
}
}
else
{
int mosthigh=highest[u];
for(int v:g[u])
{
if(v==par)continue;
if(highest[v]!=mosthigh)
{
backdfs(v,u,0);
}
else
{
if(all[u] && state==0)backdfs(v,u,0);
else backdfs(v,u,1);
}
}
}
}
void init_dfs(int u,int par)
{
highest[u]=(sheep[u] ? depth[u] : 1e9);
for(int v:g[u])
{
if(v==par)continue;
depth[v]=depth[u]+1;
init_dfs(v,u);
highest[u]=min(highest[u],highest[v]);
}
}
void bfs()
{
queue<int>q;
for(int i=1;i<=n;i++)
{
if(sheep[i])
{
q.push(i);
}
else dist[i]=-1;
}
while(q.size())
{
int u=q.front();
q.pop();
for(int v:g[u])
{
if(dist[v]!=-1)continue;
dist[v]=dist[u]+1;
q.push(v);
}
}
}
int main ()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
int sh;
cin>>n>>sh;
for(int i=1;i<n;i++)
{
int u,v;
cin>>u>>v;
g[u].push_back(v);
g[v].push_back(u);
}
for(int i=1;i<=sh;i++)
{
int u;
cin>>u;
sheep[u]=1;
}
init_dfs(1,0);
bfs();
dfs(1,0);
backdfs(1,0,0);
cout<<dp[1][0]<<"\n";
for(int u:guys)cout<<u<<" ";
cout<<"\n";
return 0;
}
