#include <bits/stdc++.h>
#define all(x) x.begin(),x.end()
#define sz(x) ((int)x.size())
#define i2 array<int,2>
#define PB push_back
using namespace std;
typedef long long ll;
const int oo = 2e9;
const int N = 500100;
vector<i2> vc;
vector<int> ans, g[N], nw_g[N], srt[N];
bool mrk[N], mrk_ans[N];
int n, k, h[N], dst[N], sh[N], up[N];
void dfs(int v, int p){
dst[v] = oo;
if (mrk[v])
dst[v] = 0;
for (int u : g[v]){
if (u == p) continue;
h[u] = h[v] + 1;
dfs(u, v);
dst[v] = min(dst[v], dst[u] + 1);
}
}
void calc_dst(int v, int p, int mn_up){
int mn1 = oo, mn2 = oo;
for (int u : g[v]){
if (u == p) continue;
if (dst[u] + 1 < mn1){
mn2 = mn1;
mn1 = dst[u] + 1;
} else if (dst[u] + 1 < mn2)
mn2 = dst[u] + 1;
}
if (mrk[v])
mn_up = 0;
dst[v] = min(dst[v], mn_up);
for (int u : g[v]){
if (u == p) continue;
int nw = oo;
if (dst[u] + 1 == mn1)
nw = min(mn_up, mn2);
else nw = min(mn_up, mn1);
calc_dst(u, v, nw + 1);
}
}
void calc_up(int v, int p){
if (v == 0)
up[v] = 0;
else {
if (dst[v] == dst[p] - 1)
up[v] = up[p];
else up[v] = v;
}
for (int u : g[v]){
if (u == p) continue;
calc_up(u, v);
}
}
void dfsik(int v){
mrk_ans[v] = 1;
for (int u : nw_g[v]){
if (mrk_ans[u]) continue;
dfsik(u);
}
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef _LOCAL
freopen("in.txt","r",stdin);
#endif // _LOCAL
cin >> n >> k;
for (int i = 1; i < n; i++){
int x, y; cin >> x >> y;
x--; y--;
g[x].PB(y);
g[y].PB(x);
}
for (int i = 0; i < k; i++){
int x; cin >> x; x--;
sh[i] = x;
mrk[x] = 1;
}
h[0] = 0;
dfs(0, -1);
calc_dst(0, -1, oo);
for (int i = 0; i < n; i++)
for (int u : g[i])
if (dst[i] - 1 == dst[u])
nw_g[i].PB(u);
calc_up(0, -1);
for (int i = 0; i < k; i++)
srt[h[sh[i]]].PB(sh[i]);
for (int ht = n - 1; ht >= 0; ht--)
for (int v : srt[ht]){
if (mrk_ans[v]) continue;
int who = up[v];
assert(!mrk_ans[who]);
ans.PB(who);
dfsik(who);
}
cout << sz(ans) << '\n';
for (int cr : ans)
cout << cr + 1 << " ";
return 0;
}
