program project1;
type
  ok = record
    etazh, okno, sosulk : integer;
  end;
var
  i : integer;
  n,m,d,k : integer;
  mass : array of ok;
  t : text;
  max, maxEtazh : integer;
  pos : integer;
  flag : boolean;

function KolSas(nomer : integer) : integer;
var kol : integer; i: integer;
begin
  kol := 0;
  for i := 0 to k-1 do begin
    if (mass[i].okno>=nomer)and(mass[i].okno<d-nomer) then
       kol := kol + mass[i].sosulk;
  end;
  KolSas := kol;
end;

begin
  pos := -1;
  max := 0; maxEtazh := 0;
  assign(t,'input.txt');
  reset(t);
  readln(t,n,m,d,k);
  setlength(mass,k);
  for I := 0 to k-1 do begin
    readln(t,mass[i].etazh,mass[i].okno,mass[i].sosulk);
    if maxEtazh<mass[i].okno then
       maxEtazh := mass[i].okno;
  end;
  close(t);
  for i := 1 to maxEtazh do begin
      if max<kolSas(i) then
         max := kolSas(i);
  end;
  for i := 1 to maxEtazh do begin
      if max=kolSas(i) then begin
         pos := i;
         break;
      end;
  end;
  assign(t,'output.txt');
  rewrite(t);
  writeln(t,pos);
  close(t);

end.