#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>using namespace std;#define maxn 300005#define INF 0x7fffffffint n,deep[maxn],dis[maxn],dis_[maxn],f[maxn],top[maxn];int head[maxn],E[maxn<<1],V[maxn<<1],W[maxn<<1],cnt,m;int path1[maxn],path2[maxn],ti[maxn],lar[maxn],size[maxn];int lca[maxn],lit_r,set[maxn];inline void in(int &now){    char Cget=getchar();now=0;    while(Cget>‘9‘||Cget<‘0‘) Cget=getchar();    while(Cget>=‘0‘&&Cget<=‘9‘)    {        now=now*10+Cget-‘0‘;        Cget=getchar();    }}void dfs1(int now,int fa){    deep[now]=deep[fa]+1,f[now]=fa,size[now]=1;    for(int i=head[now];i;i=E[i])    {        if(V[i]==fa) continue;        dis[V[i]]=W[i]+dis[now],dfs1(V[i],now),size[now]+=size[V[i]];        if(size[lar[now]]<size[V[i]]) lar[now]=V[i];    }}void dfs2(int now,int chain){    top[now]=chain,dis_[now]=dis[now]-dis[f[now]];    if(lar[now]) dfs2(lar[now],chain);else return;    for(int i=head[now];i;i=E[i])    {        if(V[i]==f[now]||V[i]==lar[now]) continue;        dfs2(V[i],V[i]);    }}void tree_lca(int op){    int x=path1[op],y=path2[op],&ci=ti[op];    ci=dis[x]+dis[y];    for(;top[x]!=top[y];)    {        if(deep[top[x]]<deep[top[y]]) swap(x,y);        x=f[top[x]];    }    if(deep[x]>deep[y]) swap(x,y);    lca[op]=x,lit_r=max(ci,lit_r);    ci-=dis[lca[op]]*2;}void dfs3(int now){    for(int i=head[now];i;i=E[i])    {        if(V[i]==f[now]) continue;        dfs3(V[i]),dis[now]+=dis[V[i]];    }    if(dis[now]==lit_r) set[++cnt]=now;}bool check(int x){    int num=0,pos=0;    memset(dis,0,4*n+4);    for(int i=1;i<=m;i++)    {        if(ti[i]>x)        {            num++;if(ti[i]>ti[pos]) pos=i;            dis[path1[i]]++,dis[path2[i]]++,dis[lca[i]]-=2;        }    }    if(!num) return true;    cnt=0,lit_r=num,dfs3(1);pos=ti[pos];    for(int i=1;i<=cnt;i++) if(pos-dis_[set[i]]<=x) return true;    return false;}int main(){    in(n),in(m);int u,v,w;    for(int i=1;i<n;i++)    {        in(u),in(v),in(w);        E[++cnt]=head[u],V[cnt]=v,W[cnt]=w,head[u]=cnt;        E[++cnt]=head[v],V[cnt]=u,W[cnt]=w,head[v]=cnt;    }    cnt=0,dfs1(1,0),dfs2(1,1);    for(int i=1;i<=m;i++) in(path1[i]),in(path2[i]),tree_lca(i);    int l=0,r=lit_r,ans=INF;lit_r=0;    while(l<=r)    {        int mid=l+r>>1;        if(check(mid)) ans=mid,r=mid-1;        else l=mid+1;    }    printf("%d\n",ans);    return 0;}