??
??:?????????????,??????????????????????????????????SN??,??????????,?????????????
??:
??SN?????????????????,?????????????????????????SN????????????????????,????????????,???????????????,??SN?????????????,?????????,????????
????,??SN????????????,?????????????????????????,???????????????????,??SN??????????,????????????????
??,??????????SN??????????????,??SN?????????,?????????????????,????????????,????????,????SN???????????
??:
????,??SN??????????????????,???????????????,???????????SN????????,?????????????,????????????????????,???????????,????SN???????????,?????????????????
?????????
???????????:??sn???????????????