Вылетает ошибка delphi

unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, math;

type
TForm1 = class(TForm)
Button1: TButton;
Edit1: TEdit;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var x,p,s,z:real; j,k:integer;
begin
s:=0;
p:=1;
z:=1.341;
x:=-0.675;
for k:=1 to 4 do s:= s+(exp(z/2*j)-exp(z/2*k)*sin((2*pi/k)+x))/
power(1+(1/(2*abs(x)*(j*j+k*k))),1/3);
for j:=3 to 7 do p:= p*((exp(-j/z*z+z)+power(abs(x+x*x*x),1/3))/
sqrt(1+sqr(z-x)+j*j))+s ;
edit1.Text:=floattostr(p);
end;

end.