code: private int sieveSearch(int limit, int start) {
          if (start >= limit)
              return -1;
  
          int index = start;
          do {
              if (!get(index))
                  return index;
              index++;
          } while(index < limit-1);
          return -1;
      }
docs: This method returns the index of the first clear bit in the search
  array that occurs at or after start. It will not search past the
  specified limit. It returns -1 if there is no such clear bit.