import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
import java.util.ArrayList;
//https://pastebin.com/vaXQ31LR
public class ccc16s3 {
    static int n, k, ans, max = 0, p;
    static boolean good[] = new boolean[200005];
    static ArrayList<Integer> adj[] = new ArrayList[200005];
    static void dfs(int N, int P){
        for (int l = 0; l < adj[N].size(); ++l){
            int next = adj[N].get(l);
            if (next == P) continue;
            dfs(next, N);
            good[N] |= good[next];
            if (good[next]) ans ++;
        }
    }
    static void get_dis(int N, int P, int D){
        if (!good[N]) return;
        for (int l = 0; l < adj[N].size(); ++l){
            int next = adj[N].get(l);
            if (next == P) continue;
            get_dis(next, N, D + 1);
        }
        if (D > max){
            p = N;
            max = D;
        }
    }
    public static void main(String[] args)
    {
        FastReader in = new FastReader();
        n = in.nextInt(); k = in.nextInt();
        for (int l = 0; l <= n; ++ l){
            adj[l] = new ArrayList<Integer>();
        }
        int a = 0;
        for (int l = 0; l < k; ++l){
            a = in.nextInt();
            good[a] = true;
        }
        int start = a;
        for (int l = 0; l < n - 1; ++l){
            a = in.nextInt(); int b = in.nextInt();
            adj[a].add(b);
            adj[b].add(a);
        }
        dfs(start, -1);
        get_dis(start, -1, 0);
        get_dis(p, -1, 0);
        //System.out.println(max);
        System.out.println(ans * 2 - max);
    }
    static class FastReader {
        BufferedReader br;
        StringTokenizer st;
        public FastReader(){
            br = new BufferedReader(new
                    InputStreamReader(System.in));
        }
        String next(){
            while (st == null || !st.hasMoreElements()){
                try {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException  e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
        int nextInt()
        {
            return Integer.parseInt(next());
        }
        long nextLong()
        {
            return Long.parseLong(next());
        }
        double nextDouble()
        {
            return Double.parseDouble(next());
        }
        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            }
            catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }
}