树链剖分+树上差分

#include<bits/stdc++.h>
using namespace std;
const int N = 5e4+10;
int n, k;
vector<int> g[N];
int fa[N], top[N], son[N], dep[N], sz[N], cnt[N], ans;
void dfs1(int x, int father){
	fa[x] = father, dep[x] = dep[father] + 1,sz[x] = 1;
	for (auto k : g[x]){
		if(k == father) continue;
		dfs1(k,x);
		sz[x] += sz[k];
		if(sz[son[x]] < sz[k]) son[x] = k;
	}
}
void dfs2(int x, int t){
	top[x] = t;
	int s = son[x];
	if(!s) return;
	dfs2(s,t);
	for(auto k : g[x]){
		if(k == fa[x] || k == s) continue;
		dfs2(k,k);
	}
}
int lca(int u, int v){
	while(top[u] != top[v]){
		if(dep[top[u]] < dep[top[v]]) swap(u,v);
		u = fa[top[u]];
	}
	return dep[u] < dep[v] ? u : v;
}

int dfs(int x, int father){
	int tot = cnt[x];
	for(auto k : g[x]){
		if(k == father) continue;
		tot += dfs(k, x);
	}
	ans = max(ans, tot);
	return tot;
}
int main(){
	cin >> n >> k;
	for (int i =1 ; i < n; i ++){
		int a, b;
		cin >> a >> b;
		g[a].push_back(b);
		g[b].push_back(a);
	}
	dfs1(1,0);
	dfs2(1,1);
	while(k --){
		int a, b;
		cin >> a >> b;
		int lc = lca(a,b);
		cnt[a] ++ , cnt[b] ++, cnt[lc] --, cnt[fa[lc]] --;
	}
	dfs(1,0);
	cout << ans;
        return 0;
}