docs: public ConciseSet convert(int... a)
    {
      ConciseSet res = empty();
      if (a != null) {
        a = Arrays.copyOf(a, a.length);
        Arrays.sort(a);
        for (int i : a) {
          if (res.last != i) {
            res.add(i);
          }
        }
      }
      return res;
    }