3

#include <bits/stdc++.h>
#define int64_t long long
using namespace std;

const int N = 1e5 + 5;
const int K = 2005;

typedef pair<int64_t, int> ii;

int n, k;
int a[N];
vector<int> graph[N];

int64_t ans;
int Visited[N], Parent[N];
int64_t mask[N];
bool check[N];

void DFS(int u) {
   Visited[u] = Visited[Parent[u]] + 1;

   if((mask[u] & (1 << Visited[u])))
      check[u] = true;
   mask[u] = mask[u] | (1 << Visited[u]);

   for(int v : graph[u]) {
      if(v != Parent[u]) {
         if(!Visited[v]) {
            Parent[v] = u;
            DFS(v);
         }
      }
   }
}

int main() {
#ifdef LOCAL
   freopen("in.txt", "r", stdin);
#else
   freopen("MILITARY.inp", "r", stdin);
   freopen("MILITARY.out", "w", stdout);
#endif
   ios_base::sync_with_stdio(false);
   cin.tie(0); cout.tie(0);

   cin >> n >> k;
   for(int i = 1; i <= k; ++i)
      cin >> a[i];

   for(int i = 1; i < n; ++i) {
        int p, q;
        cin >> p >> q;
        graph[p].push_back(q);
        graph[q].push_back(p);
   }

   for(int i = 1; i <= k; ++i) {
      fill(Visited + 1, Visited + n + 1, 0);
      fill(Parent + 1, Parent + n + 1, 0);
      DFS(a[i]);
   }

   ans = 0;
   for(int i = 1; i <= n; ++i)
      if(!check[i]) ans++;
   cout << ans << '\n';
   for(int i = 1; i <= n; ++i)
      if(!check[i])
         cout << i << ' ';

   return 0;
}