public void logout() throws Exception{
		System.out.println("α׾ƿ Ͻðڽϱ?(Y/N)");
		scan.nextLine();
		String logoutcheck = scan.nextLine();
		//缭޴ 
		if(logoutcheck.equals("Y"))
		{
			show_menu();//ʱȭ Ѿ.
		}
		else if(logoutcheck.equals("N"))
			librarian_menu();
	}