Var
 X,Y:Real;
Begin
 Writeln('To quit the program type -10 az X');
 Repeat
  Repeat
   Write('X= ');
   Readln(X);
   If (X<0) and (X<>-10) then Writeln('X out of range: negatives are forbidden!');
  Until (X>=0) or (X=-10);
  If X>4 then
   Repeat
    X:=X-4;
   Until X<=4;
  If X<>-10 then
   begin
    If X<1 then
     Y:=Sqrt(1-Sqr(X-1)) else
    If (X>=1) and (X<3) then
     Y:=1-Sqrt(1-Sqr(X-2)) else
    Y:=Sqrt(1-Sqr(X-3));
    Writeln('Y= ',Y:0:3);
   end;
 Until X=-10;
End.