var
  f:array[0..300000,0..20]of longint;
  vis:array[0..300000]of boolean;
  next,vet,dist:array[0..600000]of longint;
  head,cnt,depth,g,d,len,u,v,grand:array[0..300000]of longint;
  ans,i,j,n,m,tot,x,y,z,max,num,k,l,r,mid:longint;
  flag:boolean;
procedure add(x,y,z:longint);
begin
  inc(tot);
  next[tot]:=head[x];
  vet[tot]:=y;
  head[x]:=tot;
  dist[tot]:=z;
end;
procedure dfs(u,dep,dis:longint);
var
  i,v:longint;
begin
  depth[u]:=dep; vis[u]:=true;
  for i:=1 to 20 do
    f[u,i]:=f[f[u,i-1],i-1];
  i:=head[u];
  while i<>0 do
  begin
    v:=vet[i];
    if not vis[v] then
    begin
      f[v,0]:=u;
      d[v]:=dis+dist[i];
      dfs(v,dep+1,d[v]);
    end;
    i:=next[i];
  end;
end;
function lca(a,b:longint):longint;
var
  i,t:longint;
begin
  if depth[a]>depth[b] then begin t:=a; a:=b; b:=t; end;
  for i:=20 downto 0 do
    if depth[f[b,i]]>=depth[a] then b:=f[b,i];
  if a=b then exit(a);
  for i:=20 downto 0 do
    if f[a,i]<>f[b,i] then
      begin a:=f[a,i]; b:=f[b,i]; end;
  exit(f[a,0]);
end;
procedure getans(u,father:longint);
var
  i,v:longint;
begin
  g[u]:=cnt[u];
  i:=head[u];
  while i<>0 do
  begin
    v:=vet[i];
    if v<>father then
    begin
      getans(v,u);
      g[u]:=g[u]+g[v];
      if (g[v]=num)and(dist[i]>=k) then flag:=true;
    end;
    i:=next[i];
  end;
end;
function check(x:longint):boolean;
var
  i:longint;
begin
  flag:=false; max:=0; num:=0;
  fillchar(g,sizeof(g),0);
  fillchar(cnt,sizeof(cnt),0);
  for i:=1 to m do
    if len[i]>x then
    begin
      inc(cnt[u[i]]); inc(cnt[v[i]]);
      cnt[grand[i]]:=cnt[grand[i]]-2;
      inc(num);
      if len[i]>max then max:=len[i];
    end;
  k:=max-x;
  getans(1,0);
  exit(flag);
end;
begin
  read(n,m);
  for i:=1 to n-1 do
  begin
    read(x,y,z);
    add(x,y,z); add(y,x,z);
  end;
  dfs(1,1,0);
  for i:=1 to m do
  begin
    read(u[i],v[i]);
    grand[i]:=lca(u[i],v[i]);
    len[i]:=d[u[i]]+d[v[i]]-2*d[grand[i]];
    if len[i]>max then max:=len[i];
  end;
  l:=1; r:=max;
  while l<=r do
  begin
    mid:=(l+r)div 2;
    if check(mid) then begin r:=mid-1; ans:=mid; end else l:=mid+1;
  end;
  writeln(ans);
end.