procedure TForm1.but1Click(Sender: TObject);
begin
 txtN.Text:='1' + txtN.Text;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
 if rad1.Checked then
  begin
   memo1.Lines.Add(txtA.Text);
   txtB.Text(txtA.Text);
   txtC.Text(txtA.Text);
  end;
end;