var
 as,be,bs,ae:real;

procedure init;
 begin
  readln(as,be);
  readln(bs,ae);
 end;

procedure ik;
 var
  I,J:integer;
  flytime1,flytime2:real;
 begin
  for I:=-5 to 5 do
   begin
    if be-i<as then be:=be+24;
    flytime1:=(be-i)-as;
    if ae<bs-i then ae:=ae+24;
    flytime2:=ae-(bs-i);
    if abs(flytime1-flytime2)<1/6 then
     begin
      write(abs(I));
      halt;
     end;
   end;
 end;

begin
 init;
 ik;
end.

but how many reserved words?

main,as,try.......

and, array, as, asm, begin, case, class, const, constructor, destructor, dispinterface, div, do, downto, else, end, except, exports, file, finalization, finally, for, function, goto, if, implementation, in, inherited, initialization, inline, interface, is, label, library, mod, nil, not, object, of, or, out, packed, procedure, program, property, raise, record, repeat, resourcestring, set, shl, shr, string, then, threadvar, to, try, type, unit, until, uses, var, while, with, xor

plz read FAQ before asking such questions...