it seems all right, it says: "Wrong answer." Why?

program sum;
var a,suma,I:longint;
begin
  writeln('Vvedite chislo');
  suma:=0;
  readln(a);
    if (a<0) and (a>-10000)  then
  For i:=1 downto a do
      suma:=suma+i;
  if (a>0) and (a<10000)  then
  fOR I:=1 to a do
      suma:=suma+i;
  if (-10000<a)and(a<10000) then
  writeln(suma) else
  writeln('oshibka vvoda');
 end.