Var
 x,y:Real;
 Cp:Integer;

Begin
 Repeat
  repeat
   Write('X (0 to quit) = ');
   Readln(x);
   if x<0 then Writeln('X must be >=0!');
  until x>=0;
  Cp:=Trunc(x)+1;
  if (Cp mod 2)=1 then
   y:=Sqrt(1-Sqr(1.0*Cp-x))
  else
   y:=1-Sqrt(1-Sqr(1.0*Cp-x));
  Writeln('Y = ',y:7:5);
 Until x=0;
End.