var
at,be,bs,ae:real;

procedure init;
begin
 readln(at,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<at then flytime1:=(be+24-i)-at else flytime1:=be-i-at;
   if ae<bs-i then flytime2:=ae+24-(bs-i) else flytime2:=ae-(bs-I);
   if abs(flytime1-flytime2)<1/6 then
    begin
     write(abs(I));
     halt;
    end;
  end;
end;

begin
 init;
 ik;
end.