public String[] playList(int n) {
		TreeSet<String> set = new TreeSet<String>();
		for (int i = 1; i <= n; i++) {
			set.add(i + ".mp3");
		}
		List<String> asList = Arrays.asList(set.toArray(new String[0]));
		if (set.size() > 50) {
			asList = asList.subList(0, 50);
		}
		return asList.toArray(new String[0]);
	}