program pascal;
type matrice=array[0..151,0..3502] of longint;
     graf=array[0..151,0..151] of longint;
var s,t:matrice; px,py:array[1..8000] of longint;
    a,cost:graf; f,g:text;
    n,m,k,p,maxt:longint;

    procedure citire;
    var i,x,y,c:longint;
    begin
    assign(f,'amenzi.in'); reset(f);
    readln(f,n,m,k,p);
    for i:=1 to m do
          begin
          readln(f,x,y,c);
          inc(a[x,0]); a[x,a[x,0]]:=y; cost[x,y]:=c;
          inc(a[y,0]); a[y,a[y,0]]:=x; cost[y,x]:=c;
          end;
    for i:=1 to k do
          begin
          readln(f,x,y,c);
          inc(s[x,y],c);
          end;
    maxt:=0;
    for i:=1 to p do
       begin
       readln(f,px[i],py[i]);
       if py[i]>maxt then maxt:=py[i];
       end;
     end;

     function max(a,b:longint):longint;
     begin
     if a>b then max:=a
            else max:=b;
     end;

     procedure dinamica;
     var i,j,k,nod:longint;
     begin
     for i:=1 to n do t[i,0]:=-1;
     t[1,0]:=s[1,0];
     for i:=1 to maxt do
     for j:=1 to n do
           begin
           t[j,i]:=-1;
           if t[j,i-1]<>-1 then t[j,i]:=t[j,i-1]+s[j,i];
           for k:=1 to a[j][0] do
                   begin
                   nod:=a[j][k];
                   if (i-cost[j,nod]>-1) then
                   if (cost[j,nod]>0) and (t[nod,i-cost[j,nod]]<>-1) then
                              t[j,i]:=max(t[j,i],t[nod,i-cost[j,nod]]+s[j,i]);
                   end;
          end;
     end;

     procedure afisare;
     var i,y,x:longint;
     begin
     assign(g,'amenzi.out'); rewrite(g);
     for i:=1 to p do writeln(g,t[px[i],py[i]]);
     close(f); close(g);
     end;

     begin
     citire;
     dinamica;
     afisare;
     end.