船上共30人，每隔九个扔下一个(从一开始数，第十个扔下，在从一开始，第十个扔下，数完一圈再从头开始)，扔掉一半，求扔出的序号-A total of 30 people on board, every nine dropped a (dropped from the beginning of the tenth, from the beginning, dropped in a 10 count circle again from scratch start) throw away half, seeking to throw out of the serial number