{   prog1a.pas -- Determine Machine Epsilon
    Written Feb 20, 2001 by Eric Olson for Mathematics 483

    For more information see Step 3 in First Steps in Numerical
    Analysis, 2nd Edition, by Hosking, Joe, Joyce and Turner. }

program main;

var a,b,d,dold,x,r:real;

begin
    while not eof do begin
        read(x);
        a:=0;
        if x>0 then b:=x else b:=-x;
        d:=(a+b)/2.0;
        repeat
            r:=x+d;
            if r=x then a:=d else b:=d;
            dold:=d;
            d:=(a+b)/2.0;
        until dold=d;
        writeln('x=',x,' d=',a)
    end
end.