以下是re代码

import java.io.*;
import java.util.*;

public class Main{
    static int N = 60010,M = 2*N;
    static int[] h = new int[N],e = new int[M],ne = new int[M];
    static int[] depth = new int[N],sum = new int[N];
    static int[][] fa = new int[N][30];
    static int idx = 0,INF = 0x3f3f3f3f,n,m,max = 0;
    static BufferedReader br 
        = new BufferedReader(new InputStreamReader(System.in));
    static StreamTokenizer sc = new StreamTokenizer(br);
    public static void main(String[] args)throws IOException{
        n = nextRead();
        m = nextRead();
        Arrays.fill(h,-1);
        for(int i = 0;i<n-1;i++){
            int a = nextRead();
            int b = nextRead();
            add(a,b);
            add(b,a);
        }
        
        bfs();
        
        for(int i = 1;i<=m;i++){
            int a = nextRead();
            int b = nextRead();
            int anc = lca(a,b);
            sum[a]++;
            sum[b]++;
            sum[anc]--;
            sum[fa[anc][0]]--;
        }
        
        dfs(1,0);
        System.out.println(max);
    }
    public static void dfs(int u,int fa){
        for(int i = h[u];i!=-1;i = ne[i]){
            int j = e[i];
            if(j == fa) continue;
            dfs(j,u);
            sum[u]+=sum[j];
        }
        max = Math.max(max,sum[u]);
    }
    public static int lca(int a,int b){
        if(depth[a]<depth[b]){
            int c = a;
            a = b;
            b = c;
        }
        for(int k = 19;k>=0;k--)
            if(depth[fa[a][k]]>=depth[b])
                a = fa[a][k];
        if(a == b) return a;
        for(int k = 19;k>=0;k--)
            if(fa[a][k]!=fa[b][k]){
                a = fa[a][k];
                b = fa[b][k];
            }
            
        return fa[a][0];
    }
    public static void bfs(){
        Arrays.fill(depth,INF);
        depth[0] = 0;
        depth[1] = 1;
        Queue<Integer> q = new LinkedList<>();
        q.add(1);
        while(!q.isEmpty()){
            int t = q.poll();
            for(int i = h[t];i!=-1;i = ne[i]){
                int j = e[i];
                if(depth[j]>depth[t]+1){
                    depth[j] = depth[t]+1;
                    q.add(j);
                    fa[j][0] = t;
                    for(int k = 1;k<=19;k++)
                        fa[j][k] = fa[fa[j][k-1]][k-1];
                }
            }
        }
    }
    public static void add(int a,int b){
        e[idx] = b;
        ne[idx] = h[a];
        h[a] = idx++;
    }
    public static int nextRead()throws IOException{
        sc.nextToken();
        return (int)sc.nval;
    }
}