public List<Integer> getVariables(){
		List<Integer> vars = new ArrayList<>();
		for (int i = 0; i < size(); i++) {
			Clause clause = get(i);
			for (int j = 0; j < clause.size(); j++) {
				int var = Math.abs(clause.get(j));
				if(!vars.contains(var)){
					vars.add(var);
				}
			}
		}
		return vars;
	}