#include<bits/stdc++.h>
using namespace std;
const int N=3e5+10;
int read(){
	int x=0,f=1;char ch=getchar();
	while(!isdigit(ch)){if(ch=='-')f=-1;ch=getchar();}
	while(isdigit(ch)){x=x*10+ch-'0';ch=getchar();}
	return x*f;
}
int n,m,s[N],e[N];
int cnt,pre[N];
int f[N][20],lg[N],w[N][20],dep[N],dis[N];
struct node{
	int to,next,len;
}a[N*2];
void add(int x,int y,int l){
	a[++cnt]={y,pre[x],l};
	pre[x]=cnt;
}
void dfs(int x,int path){
	f[x][0]=path;
	dep[x]=dep[path]+1;
	for(int i=pre[x];i;i=a[i].next){
		if(a[i].to==path)continue;
		w[a[i].to][0]=a[i].len;
		dfs(a[i].to,x);
	}
}
int luj(int x,int y){
	int ans=0;
	if(dep[x]<dep[y])swap(x,y);
	while(dep[x]>dep[y]){
		ans+=w[x][lg[dep[x]-dep[y]]];
		x=f[x][lg[dep[x]-dep[y]]];
	}
	if(x==y)return ans;
	for(int i=lg[dep[x]];i>=0;i--)if(f[x][i]!=f[y][i]){
		ans+=w[x][i]+w[y][i];
		x=f[x][i],y=f[y][i];
	}
	ans+=w[x][0]+w[y][0];
	return ans;
}
int lca(int x,int y){
	if(dep[x]<dep[y])swap(x,y);
	while(dep[x]>dep[y])x=f[x][lg[dep[x]-dep[y]]];
	if(x==y)return x;
	for(int i=lg[dep[x]];i>=0;i--)if(f[x][i]!=f[y][i])x=f[x][i],y=f[y][i];
	return f[x][0];
}
int maxx,cha[N],ed[N];
void dfs2(int x,int path){
	for(int i=pre[x];i;i=a[i].next){
		if(a[i].to==path)continue;
		dfs2(a[i].to,x);
		cha[x]+=cha[a[i].to];
		ed[i]=cha[a[i].to];
	}
}
bool check(int mid){
	memset(cha,0,sizeof(cha));
	memset(ed,0,sizeof(ed));
	int t=0;
	for(int i=1;i<=m;i++)
		if(dis[i]>mid){
			cha[s[i]]++;
			cha[e[i]]++;
			cha[lca(s[i],e[i])]-=2;
			t++;
		}
	if(t==0)return true;
	dfs2(1,0);
	int ans=0;
	for(int i=1;i<=2*(n-1);i++)if(ed[i]==t)ans=max(ans,a[i].len);
	if(maxx-ans<=mid)return true;
	return false;
}
signed main(){
	for(int i=2;i<N;i++)lg[i]=lg[i/2]+1;
	n=read(),m=read();
	int r=0,l=0,ans=0;
	for(int i=1;i<n;i++){
		int u=read(),v=read(),c=read();
		add(u,v,c);
		add(v,u,c);
	}
	dfs(1,0);
	for(int j=1;j<=lg[n];j++){
		for(int i=1;i<=n;i++)f[i][j]=f[f[i][j-1]][j-1],w[i][j]=w[i][j-1]+w[f[i][j-1]][j-1];
	}
	for(int i=1;i<=m;i++){
		s[i]=read(),e[i]=read();
		dis[i]=luj(s[i],e[i]);
		maxx=max(maxx,dis[i]);
	}
	int ma=0;
	for(int i=1;i<=2*(n-1);i++)ma=max(ma,a[i].len);
	r=maxx;
	l=maxx-ma;
	while(l<=r){
		int mid=(l+r)>>1;
		if(check(mid))ans=mid,r=mid-1;
		else l=mid+1;
	}
	cout<<ans;
	return 0;
}