synchronized public String giveBack(Long i) {
		if (i.longValue() == latest) {
			shrinkLatest();
		}
		
		freeSequences.add(i);
		String s = currentSequences.get(i);
		currentSequences.remove(i);
		if (currentSequences.size() == 0) {
			latest = 0;
		}
		return s;
	}