?? ????????????????:??,??????????
????:1???????????:????sn????
2???????????
3???????
4???????????
5?????????
?12???????????2????????????
?????????????????:??????????,????????????????,??,??????????«???»??,???????????3??“??????”?????????,????????????????????????????????????
????????????????,????,????????,?????
?????,???,??????????????,??,???????(???????? ????????)
????????????????:???????????????