program Project15a;

{$APPTYPE CONSOLE}

uses
  SysUtils;
  var
    n,k,i,a,b,c,d:integer;
    left,right,per:extended;
  function cubroot(x:extended):extended;
      begin
        result:=(a*x*x*x)+(x*x*b)+(c*x)+d;
      end;
begin
  //reset(input,'cubroot.in');
  //rewrite(output,'cubroot.out');
  read(a,b,c,d);
  left:=-1000;
  right:=1000;
  for i:=1 to 60 do
    begin
      per:=(right+left)/2;
      if cubroot(per)>0 then right:=per;
      if cubroot(per)<0 then left:=per;
      if cubroot(left)=0 then
        begin
          write(left);
          exit;
        end;
      if cubroot(right)=0 then
        begin
          write(right);
          exit;
        end;
    end;
  write(per);
  readln;
  readln;
end.