public int add(Student student) {
		int i;
		boolean error = false;
		for (i = 0; i < list.size(); i++) {
			if (list.get(i).getId() == student.getId()) {
				error = true;
			}
		}
		if (error) {
			System.out.println("Error : Same ID in the Promotion !");
		} else {
			list.add(student);
			if (student.getP() != null) {
				student.setP(null);
			}
			student.setP(this);
			return 1;
		}
		return 0;
	}