#include <bits/stdc++.h>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//#pragma GCC optimize("-O3")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC optimize("-Ofast")
#define N 500050
#define NN 1005000
#define PB push_back
#define endl '\n'
#define pri(x) cout << x << endl
#define _ << " " <<
#define all(x) x.begin(), x.end()
#define sz(x) int(x.size())
#define M ll(1e9 + 7)
#define F first
#define S second
using namespace std;
//using namespace __gnu_pbds;
typedef long long ll;
typedef long double ld;
typedef short int si;
typedef unsigned long long ull;
//typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
//ordered_set se;
int n, k;
bool mk[N], mkr[N];
set <int> g[N];
vector <pair <int, int> > who[N];
int main()
{
ios_base::sync_with_stdio(0); istream::sync_with_stdio(0); cin.tie(0); cout.tie(0);
// freopen("1.in", "r", stdin);
//
// freopen("1.out", "w", stdout);
cin >> n >> k;
for (int i = 1; i < n; i++)
{
int x, y;
cin >> x >> y;
g[x].insert(y);
g[y].insert(x);
}
for (int i = 0; i < k; i++)
{
int x;
cin >> x;
mk[x] = 1;
}
queue <int> qr;
for (int i = 1; i <= n; i++)
{
if (mk[i])
{
mkr[i] = 1;
who[i].PB({i, 0});
}
if (sz(g[i]) == 1)
{
qr.push(i);
}
}
while (sz(qr))
{
int v = qr.front();
qr.pop();
int u = *g[v].begin();
g[v].clear();
g[u].erase(v);
vector <pair <int, int> > cur; cur.clear();
int i = 0, j = 0;
while (i < sz(who[u]) || j < sz(who[v]))
{
pair <int, int> pt;
if (j < sz(who[v]) && (i == sz(who[u]) || who[u][i].S > who[u][j].S))
{
pt = who[v][j++];
pt.S++;
}
else
pt = who[u][i++];
if (sz(cur) == 1 && cur.back().S == pt.S)
{
mkr[pt.F] = 0;
mkr[cur.back().F] = 0;
mkr[u] = 1;
cur.back().F = u;
continue;
}
else
cur.PB(pt);
}
if (sz(g[u]) == 1)
qr.push(u);
who[u] = cur;
}
vector <int> ans; ans.clear();
for (int i = 1; i <= n; i++)
if (mkr[i])
ans.PB(i);
pri(sz(ans));
for (auto it : ans)
cout << it << " ";
}
