#include <bits/stdc++.h> using namespace std; using ll = long long; using ld = long double; #define fi first #define se second #define vi vector<int> #define vll vector<long long> #define pii pair<int, int> #define pll pair<long long, long long> #define pb push_back #define mp make_pair #define eb emplace_back #define all(x) (x).begin(), (x).end() #define sz(x) (int)(x).size() mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count()); mt19937_64 rng64(chrono::high_resolution_clock::now().time_since_epoch().count()); inline int rand(int l,int r){return uniform_int_distribution<int>(l, r)(rng);} inline ll rand(ll l,ll r){return uniform_int_distribution<ll>(l, r)(rng64);} #ifdef DEBUG auto&operator<<(auto&o,pair<auto,auto>p){return o<<"("<<p.first<<", "<<p.second<<")";} auto operator<<(auto&o,auto x)->decltype(x.end(),o){o<<"{";int i=0;for(auto e:x)o<<","+!i++<<e;return o<<"}";} #define debug(X...)cerr<<"["#X"]: ",[](auto...$){((cerr<<$<<"; "),...)<<endl;}(X) #else #define debug(...){} #endif struct custom_hash { static uint64_t splitmix64(uint64_t x) { x += 0x9e3779b97f4a7c15; x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9; x = (x ^ (x >> 27)) * 0x94d049bb133111eb; return x ^ (x >> 31); } size_t operator()(uint64_t x) const { static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count(); return splitmix64(x + FIXED_RANDOM); } }; struct pair_hash{ size_t operator()(const pair<int,int>&x)const{ return hash<long long>()(((long long)x.first)^(((long long)x.second)<<32)); } }; const int MAXN = 5e5 + 7; vi g[MAXN]; int f[MAXN]; int dist[MAXN]; int n, k; vi ans = {}; pii dfs(int v, int p){ int curr = (dist[v] == 0 ? 0 : -1); int up = -1; for(auto u : g[v]){ if(u == p){ continue; } pii ret = dfs(u, v); if(ret.fi != -1){ curr = ret.fi + 1; }else if(ret.se != -1){ up = max(up, ret.se - 1); } } //cout << v << ' ' << curr << ' ' << up << '\n'; if(up >= curr || curr == -1){ return mp(-1, up); } if(p != v && dist[p] == curr + 1){ return mp(curr, -1); }else{ // cout << "BUILD: " << v << '\n'; ans.pb(v); return mp(-1, curr); } } int main(){ ios_base::sync_with_stdio(0); cin.tie(NULL); cout.tie(NULL); cin >> n >> k; for(int i = 1; i < n; i++){ int a, b; cin >> a >> b; g[a].pb(b); g[b].pb(a); } queue<int> q; for(int i = 1; i <= k; i++){ int x; cin >> x; f[x] = 1; dist[x] = 0; q.push(x); } while(sz(q)){ int v = q.front(); q.pop(); for(auto u : g[v]){ if(f[u]){ continue; } f[u] = 1; dist[u] = dist[v] + 1; q.push(u); } } dfs(1, 1); cout << sz(ans) << '\n'; for(auto ele : ans){ cout << ele << ' '; } cout << '\n'; return 0; }