#include<iostream>

#include<cstdio>

#include<cstring>

#include<vector>

#include<algorithm>

using namespace std;

const int N=3e5+;

int n,m,head[N],xnt,cs[N],bh[N],l,r,mx,fa[N],hd[N],xt,dis[N],nw,mid,ans;

bool vis[N],flag;

struct Ques{

    int dis,x,y,lca;

}a[N];

struct Edge{

    int next,to,w;

    Edge(int n=,int t=,int w=):next(n),to(t),w(w) {}

}edge[N<<],ed[N<<];

void add(int x,int y,int z)

{

    edge[++xnt]=Edge(head[x],y,z);head[x]=xnt;

    edge[++xnt]=Edge(head[y],x,z);head[y]=xnt;

}

void ad(int x,int y,int z)

{

    ed[++xt]=Edge(hd[x],y,z);hd[x]=xt;

    ed[++xt]=Edge(hd[y],x,z);hd[y]=xt;

}

int find(int a){return fa[a]==a?a:fa[a]=find(fa[a]);}

bool cmp(Ques a,Ques b){return a.dis>b.dis;}

void tarjan(int cr,int f)

{

    vis[cr]=;

    for(int i=hd[cr],v;i;i=ed[i].next)

        if(vis[v=ed[i].to])

        {

            int k=ed[i].w,lc=find(v);

            a[k].lca=lc;a[k].dis=dis[cr]+dis[v]-*dis[lc];

            mx=max(mx,a[k].dis);

        }

    for(int i=head[cr],v;i;i=edge[i].next)

        if((v=edge[i].to)!=f)

        {

            bh[v]=i;

            dis[v]=dis[cr]+edge[i].w;

            tarjan(v,cr);fa[v]=cr;

        }

}

void solve(int cr)

{

    cs[a[cr].x]++;cs[a[cr].y]++;cs[a[cr].lca]-=;

}

int dfs(int cr,int f)

{

    int ret=cs[cr];

    for(int i=head[cr],v;i;i=edge[i].next)

        if((v=edge[i].to)!=f)

        {

            ret+=dfs(v,cr);if(flag)return ;

        }

    if(ret==nw&&mx-edge[bh[cr]].w<=mid)flag=;

    return ret;

}

int main()

{

    scanf("%d%d",&n,&m);int x,y,z;

    for(int i=;i<n;i++)

    {

        scanf("%d%d%d",&x,&y,&z);add(x,y,z);

        fa[i]=i;

    }

    fa[n]=n;

    for(int i=;i<=m;i++)

    {

        scanf("%d%d",&a[i].x,&a[i].y);ad(a[i].x,a[i].y,i);

    }

    tarjan(,);sort(a+,a+m+,cmp);r=mx;

    while(l<=r)

    {

        mid=((l+r)>>);memset(cs,,sizeof cs);

        for(nw=;nw<=m&&a[nw].dis>mid;nw++)solve(nw);

        nw--;flag=;dfs(,);

        if(flag)ans=mid,r=mid-;

        else l=mid+;

    }

    printf("%d",ans);

    return ;

}