树上差分板子:
#include <cmath>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#define db double
#define sg string
#define ll long long
#define rep(i,x,y) for(ll i=(x);i<=(y);i++)
#define red(i,x,y) for(ll i=(x);i>=(y);i--)
using namespace std;
const ll N=5e4+5;
const ll Inf=1e18;
ll n,m,ans,v[N],dep[N],fa[N][20];
ll cnt,to[N<<1],nxt[N<<1],head[N];
inline ll read() {
ll x=0;char ch=getchar();bool f=0;
while(ch>'9'||ch<'0'){if(ch=='-')f=1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=(x<<1)+(x<<3)+ch-'0';ch=getchar();}
return f?-x:x;
}
inline void write(ll x) {
if(x<0) putchar('-');
if(x>9) write(x/10);
putchar(x%10+48);
}
void ins(ll x,ll y) {
to[++cnt]=y;nxt[cnt]=head[x];head[x]=cnt;
}
void dfs(ll x) {
dep[x]=dep[fa[x][0]]+1;
rep(i,1,19) fa[x][i]=fa[fa[x][i-1]][i-1];
for(ll i=head[x];i;i=nxt[i]) {
ll y=to[i];
if(y!=fa[x][0]) {
fa[y][0]=x;dfs(y);
}
}
}
ll lca(ll x,ll y) {
if(dep[x]<dep[y]) swap(x,y);
ll dlt=dep[x]-dep[y];
rep(i,0,19) if(dlt&(1<<i)) x=fa[x][i];
if(x==y) return y;
red(i,19,0) if(fa[x][i]!=fa[y][i]) x=fa[x][i],y=fa[y][i];
return fa[x][0];
}
void _dfs(ll x) {
for(ll i=head[x];i;i=nxt[i]) {
ll y=to[i];
if(y!=fa[x][0]) {
_dfs(y);v[x]+=v[y];
}
}
ans=max(ans,v[x]);
}
int main() {
n=read(),m=read();
rep(i,2,n) {
ll x=read(),y=read();
ins(x,y),ins(y,x);
}
dfs(1);
rep(i,1,m) {
ll x=read(),y=read(),z=lca(x,y);
++v[x],++v[y];
--v[z],--v[fa[z][0]];
}
_dfs(1);
write(ans);
return 0;
}