????:1?????????:????????

2???????

3??????????

4?????sn

5??????

???????????????11?????????29?????????? ??????,?????????,?????????????????????,??????????????????????????????

??,??,???????,????,???;???????????,??????;????,?????????,????????????????????????????,????????????????????????

???????????????,??????,????????,????,?????????????,?????????????«???»«????????????????»«????»?????????????,???????????,??????;????????????????????;??;????????????,?????????????????

?????????:????