program amenzi;
  const
    fin='amenzi.in';
    fout='amenzi.out';
    inf=maxint;
    nmax=150;
  type
    coada=^elem;
    elem=record
      nod:integer;t:longint;
      sum:longint;
      last:integer;
      urm:coada;
    end;
    amenda=record
      n,t,sum:longint;
      end;
  var
    d:array[1..nmax,1..nmax] of longint;
    m,n,p,i,j,k,x,y,c,ind:longint;
    cap,aux,q,ult:coada;
    am:array[1..12000] of amenda;
    max:longint;
    meet:array[1..8000] of record
      n,t:longint;
    end;

begin
  assign(input,fin);
    reset(input);
    readln(n,m,k,p);
    for i:=1 to n do
      for j:=1 to n do
        d[i,j]:=inf;
    for i:=1 to n do
      d[i,i]:=0;
    for i:=1 to m do
      begin
        readln(x,y,c);
        d[x,y]:=c;
        d[y,x]:=c;
      end;
    for i:=1 to k do
      begin
        readln(am[i].n,am[i].t,am[i].sum);
      end;
    for i:=1 to p do
      readln(meet[i].n,meet[i].t);
  close(input);
  assign(output,fout);
    rewrite(output);
    for x:=1 to n do
      for i:=1 to n do
        for j:=1 to n do
          if d[i,x]+d[x,j]<d[i,j] then
            d[i,j]:=d[i,x]+d[x,j];
    for ind:=1 to p do
      if d[1,meet[ind].n]<=meet[ind].t then
      begin
        new(cap);
        cap^.nod:=1;cap^.t:=0;cap^.sum:=0;cap^.urm:=nil;
        max:=0;
        ult:=cap;
        cap^.last:=0;
        while cap<>nil do
          begin
            for i:=1 to k do
              begin
                if am[i].t+d[am[i].n,meet[ind].n]<=meet[ind].t then
                  if cap^.t+d[cap^.nod,am[i].n]<=am[i].t then
                    if cap^.last<>i then
                    begin
                      new(q);
                      ult^.urm:=q;q^.urm:=nil;
                      q^.nod:=am[i].n;
                      q^.t:=am[i].t;
                      q^.sum:=cap^.sum+am[i].sum;
                      q^.last:=i;
                      ult:=q;
                      if q^.sum>max then
                        max:=q^.sum;
                    end;
              end;
            q:=cap;
            cap:=cap^.urm;
            dispose(q);
          end;
        writeln(max);
      end
    else
      writeln('-1');
  close(output);
end.