procedure TForm1.Button1Click(Sender: TObject);
var a,b,c : Integer;
begin
 a := StrToInt(Edit1.Text);
 b := StrToInt(Edit2.Text);
 c := a + b;
 Edit3.Text := IntToStr(c);
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
 Edit1.Text := ''; Edit2.Text := '';
 Edit3.Text := '';
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
 Close;
end.