#include <bits/stdc++.h>
using namespace std;
const int maxn = 5e5 + 5;
int d[maxn];
int n, k;
vector<int> g[maxn];
int mark[maxn];
int dep[maxn];
int par[maxn];
int used[maxn];
int X[maxn];
bool cmp(int a, int b)
{
return dep[a] > dep[b];
}
void dfs(int x, int p)
{
dep[x] = dep[p] + 1;
par[x] = p;
for (auto v : g[x])
{
if (v == p)
continue;
dfs(v, x);
}
}
void bfs()
{
queue<int> q;
for (int i = 1; i <= n; i++)
{
d[i] = -1;
}
for (int i = 0; i < k; i++)
{
d[X[i]] = 0;
q.push(X[i]);
}
while (!q.empty())
{
auto x = q.front();
// cout << x << " " << d[x] << endl;
q.pop();
for (auto v : g[x])
{
if (d[v] != -1)
continue;
d[v] = d[x] + 1;
q.push(v);
}
}
}
void clear(int x)
{
mark[x] = 1;
for (auto v : g[x])
{
if (mark[v] || d[v] != d[x] - 1)
continue;
clear(v);
}
}
vector<int> ans;
int main()
{
ios::sync_with_stdio(false);
cin.tie(0);
cin >> n >> k;
for (int i = 0; i < n - 1; i++)
{
int a, b;
cin >> a >> b;
g[a].push_back(b);
g[b].push_back(a);
}
for (int i = 0; i < k; i++)
cin >> X[i];
dfs(1, 0);
bfs();
sort(X, X + k, cmp);
for (int i = 0; i < k; i++)
{
if (mark[X[i]])
continue;
int crr = X[i];
while (par[crr] && d[par[crr]] == d[crr]+1)
crr = par[crr];
ans.push_back(crr);
clear(crr);
}
cout << ans.size() << "\n";
for (auto v : ans)
cout << v << " ";
}
