static void qsort(long[] arr) {
    Long[] oarr = new Long[arr.length];
    for (int i = 0; i < arr.length; i++) {
      oarr[i] = arr[i];
    }

    ArrayList<Long> alist = new ArrayList<Long>(Arrays.asList(oarr));
    Collections.sort(alist);

    for (int i = 0; i < arr.length; i++) {
      arr[i] = alist.get(i);
    }
}