#include <iostream>

 #include <cstring>

 #include <cstdio>

 #include <algorithm>

 #include <ctime>

 #include <cstdlib>

 using namespace std;

 const int Maxn=;

 const int Inf=0x3f3f3f3f;

 int n,m,u,v,w,cnt,tot,MaxLen,MinLen,Minw,Maxw,Ans;

 int head[Maxn],dep[Maxn],siz[Maxn],father[Maxn],W[Maxn],p[Maxn],q[Maxn],dis[Maxn],Len[Maxn],c[Maxn],top[Maxn],Memory[Maxn],Root;

 struct Edge{int to,next,w;}edge[Maxn<<];

 inline void Get_Int(int &x)

 {

     x=;  char ch=getchar(); int f=;

     while (ch<'' || ch>'') {if (ch=='-') f=-; ch=getchar();}

     while (ch>='' && ch<='') {x=x*+ch-''; ch=getchar();} x*=f;

 }

 inline void Put_Int(int x)

 {

     char ch[];  int top=;

     if (x==) ch[++top]='';

     while (x) ch[++top]=x%+'',x/=;

     while (top) putchar(ch[top--]); putchar('\n');

 }

 inline int Max(int x,int y) {return x>y?x:y;}

 inline int Min(int x,int y) {return x>y?y:x;}

 inline void Add(int u,int v,int w)

 {edge[cnt].to=v;edge[cnt].next=head[u];edge[cnt].w=w;head[u]=cnt++;}

 //==============================================

 void Dfs1(int u,int fa)

 {

     siz[u]=;

     for (int i=head[u];i!=-;i=edge[i].next)

         if (edge[i].to!=fa)

         {

             dep[edge[i].to]=dep[u]+;

             father[edge[i].to]=u;

             dis[edge[i].to]=dis[u]+edge[i].w;

             W[edge[i].to]=edge[i].w;

             Dfs1(edge[i].to,u);

             siz[u]+=siz[edge[i].to];

         }

 }

 void Dfs2(int u,int chain,int fa)

 {

     top[u]=chain;  int k=;

     for (int i=head[u];i!=-;i=edge[i].next)

         if (edge[i].to!=fa && (siz[edge[i].to]>siz[k] || k==)) k=edge[i].to;

     if (k==) return;

     Dfs2(k,chain,u);

     for (int i=head[u];i!=-;i=edge[i].next)

         if (edge[i].to!=fa && k!=edge[i].to) Dfs2(edge[i].to,edge[i].to,u);

 }

 inline int Lca(int u,int v)

 {

     while (true)

     {

         if (top[u]==top[v]) return dep[u]>dep[v]?v:u;

         if (dep[top[u]]>dep[top[v]]) u=father[top[u]]; else v=father[top[v]];

     }

 }

 int Get(int u,int f)

 {

     for (int i=head[u];i!=-;i=edge[i].next)

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

             c[u]+=Get(edge[i].to,u);

     if (c[u]==tot) MinLen=Max(MinLen,W[u]);

     return c[u];

 }

 inline bool Check(int t)

 {

     MaxLen=MinLen=tot=;

     memset(c,,sizeof(c));

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

         if (Len[i]>t)

         {

             c[p[i]]++,c[q[i]]++;

             c[Lca(p[i],q[i])]-=;

             MaxLen=Max(MaxLen,Len[i]);

             tot++;

         }

     if (Memory[tot])

     {

         if (Memory[tot]<=t) return true;

         return false;

     }

     Get(Root,Root);

     Memory[tot]=(MaxLen-MinLen);

     if (Memory[tot]<=t) return true;

     return false;

 }

 int main()

 {

     srand(time());

     Get_Int(n),Get_Int(m);

     memset(head,-,sizeof(head)); Minw=Inf;

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

     {

         Get_Int(u),Get_Int(v),Get_Int(w);

         Add(u,v,w),Add(v,u,w);

         Minw=Min(Minw,w);

     }

     for (int i=;i<=m;i++) Get_Int(p[i]),Get_Int(q[i]);

     Root=rand()%n+;

     father[Root]=Root; dep[Root]=; dis[Root]=;

     Dfs1(Root,Root);

     Dfs2(Root,Root,Root);

     memset(Memory,,sizeof(Memory));

     for (int i=;i<=m;i++) Len[i]=dis[p[i]]+dis[q[i]]-*dis[Lca(p[i],q[i])],Maxw=Max(Maxw,Len[i]);

     int l=Minw,r=Maxw;

     while (l<=r)

     {

         int mid=(l+r)>>;

         if (Check(mid)) Ans=mid,r=mid-; else l=mid+;

     }

     Put_Int(Ans);

     return ;

 }