#include<bits/stdc++.h>
using namespace std;
using ll=long long;
const int N=5e5+7;
struct EDGE{
	int to;
	int next;
}edge[N*2];
int head[N*2],cnt,D[N],ans,lans;
int fa[N][25];
int deep[N];
void init(){
	for(int i=0;i<2*N;i++){
		edge[i].next=-1;
		head[i]=-1;
	}
	cnt=0;
}
void addedge(int u,int v){
	edge[cnt].to=v;
	edge[cnt].next=head[u];
	head[u]=cnt++;
}
void dfsa(int x,int father){
	deep[x]=deep[father]+1;
	fa[x][0]=father;
	for(int i=1;(1<<i)<=deep[x];i++){
		fa[x][i]=fa[fa[x][i-1]][i-1];
	}
	for(int i=head[x];~i;i=edge[i].next){
		if(edge[i].to!=father){
			dfsa(edge[i].to,x);
		}
	}
}
int LCA(int x,int y){
	if(deep[x]<deep[y]) swap(x,y);
	for(int i=19;i>=0;i--){
		if(deep[x]-(1<<i)>=deep[y]){
			x=fa[x][i];
		}
	}
	if(x==y) return x;
	for(int i=19;i<=0;i--){
		if(fa[x][i]!=fa[y][i]){
			x=fa[x][i];
			y=fa[y][i];
		}
	}
	return fa[x][0];
}
void dfsb(int u,int fath){
	for(int i=head[u];~i;i=edge[i].next){
		int e=edge[i].to;
		if(e==fath){
			continue;
		}
		dfsb(e,u);
		D[u]+=D[e];
	}
	ans=max(ans,D[u]);
}
int main(){
	init();
	int n,m;
	scanf("%d%d",&n,&m);
	for(int i=1;i<n;i++){
		int u,v;
		scanf("%d%d",&u,&v);
		addedge(u,v);
		addedge(v,u);
	}
	dfsa(1,0);
	for(int i=1;i<=m;i++){
		int a,b;
		scanf("%d%d",&a,&b);
		int lcans=LCA(a,b);
		D[a]++;
		D[b]++;
		D[lcans]--;
		D[fa[lcans][0]]--;
	}
	dfsb(1,0);
	printf("%d",ans);
	return 0;
}