#include<bits/stdc++.h>

 using namespace std;

 #define fu(a,b,c) for(int a=b;a<=c;++a)

 #define fd(a,b,c) for(int a=b;a>=c;--a)

 int read(){

   int ans=,w=;char c=getchar();

   while(!isdigit(c)&&c!='-')c=getchar();

   if(c=='-')w=-,c=getchar();

   while(isdigit(c))ans=(ans<<)+(ans<<)+c-'',c=getchar();

   return ans*w;

 }

 const int N=3e5+;

 struct Edge{int v,w,next;}E[N<<];

 int head[N],tot=;

 int n,m,l=,r=;

 int cost[N],fro[N],to[N],lca[N];

 int dis[N],dep[N],cnt[N],pre[N];

 int fa[N][],Log2[N];

 void add(int u,int v,int w){E[++tot]=(Edge){v,w,head[u]};head[u]=tot;}

 void dfs(int u){

   dep[u]=dep[fa[u][]]+;

   fu(i,,Log2[dep[u]])fa[u][i]=fa[fa[u][i-]][i-];

   for(int i=head[u];i;i=E[i].next){

     int v=E[i].v;

     if(v==fa[u][])continue;

     pre[v]=i;

     fa[v][]=u;

     dis[v]=dis[u]+E[i].w;

     dfs(v);

   }

 }

 void redfs(int u){

   for(int i=head[u];i;i=E[i].next){

     int v=E[i].v;

     if(v==fa[u][])continue;

     redfs(v);

     cnt[u]+=cnt[v];

   }

 }

 int LCA(int x,int y){

   if(dep[x]<dep[y])swap(x,y);

   int t=dep[x]-dep[y];

   fu(i,,Log2[t])if(t&(<<i))x=fa[x][i];

   if(x==y)return x;

   int k=Log2[dep[x]];

   while(fa[x][]!=fa[y][]){

     if(fa[x][k]!=fa[y][k]){

       x=fa[x][k];

       y=fa[y][k];

     }

     k--;

   }

   return fa[x][];

 }

 bool check(int vl){

   int siz=;

   fu(i,,n)cnt[i]=;

   fu(i,,m){

     if(cost[i]<=vl)continue;

     siz++;

     cnt[fro[i]]++;

     cnt[to[i]]++;

     cnt[lca[i]]-=;

   }

   redfs();

   int maxv=;

   fu(i,,n){

     if(cnt[i]!=siz)continue;

     maxv=max(maxv,E[pre[i]].w);

   }

   fu(i,,m)if(cost[i]-maxv>vl)return ;

   return ;

 }

 int main(){

   n=read();m=read();

   Log2[]=;fu(i,,n)Log2[i]=Log2[i>>]+;

   fu(i,,n-){

     int u=read(),v=read(),w=read();

     add(u,v,w);

     add(v,u,w);

   }

   dfs();

   fu(i,,m){

     fro[i]=read(),to[i]=read();

     lca[i]=LCA(fro[i],to[i]);

     cost[i]=dis[fro[i]]+dis[to[i]]-(dis[lca[i]]<<);

     r=max(r,cost[i]);

   }

   int ans;

   while(l<=r){

     int mid=(l+r*)/;

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

     else l=mid+;

   }

   printf("%d",ans);

   return ;

 }