var
 AD,AC,BD,BC,X,Y:int64;
 CD:real;

BEGIN
 read(AD,AC,BD,BC);

 X:=AD*AC-BD*BC;
 Y:=AD*AC*(BD*BD+BC*BC)-BD*BC*(AD*AD+AC*AC);
 if(X=0)or(Y*X<0) then write('Impossible.')
 else begin
  write('Distance is ');
  CD:=1000*sqrt(Y/X);
  write(CD:0:0,' km.');
 end;
END.