deret bilangan prima

Program bil_prima;
uses crt;

var
a,b,c,d : integer;

BEGIN clrscr;
      write('Masukan Bilangan Prima sampai : '); readln(d);
      for a:= 1 to d do
      Begin;
      c:=0;
      for b:=1 to a do
      Begin;
      if a mod b=0 then
      c:=c+1;
      end;

      if c=2 then
      begin;
      write(a,' ');
      write('');
      end;
      end;

      readln;
END.

END.