public IntegerAggregate getDistanceBetween(Integer start, Integer finish)
  {
    if (start > maxStart || finish > maxTarget)
    {
      logger.warning("Invalid request, out of range (from: " + start + " to: " + finish);
      throw new IndexOutOfBoundsException("Unable to find value for " + start + " -> " + finish);
    }
    return getDistance(getNode(start), getNode(finish));
  }