????:1???????sn:????????

2???????????????

3???????????

4?????

5???????????

?????7???19??????????????? (?? ???????)??????????????19?,?????????,??????????3??(??????????,??)?,????

????,??????18??,???????20????,???????????????????386??411??,??????3??????????,?????

???????????,??5??????????????????????,?????????????????????,??,?????????????,??????????????????????,??????????????????????????“????????????”??,20??????

????,????????????,??????????????????1.5?????????,??,???????????(???????) ???????????:???