Posted by haifeng on 2011-04-28 22:33:34 last update 0000-00-00 00:00:00 | Edit | Answers (1)
1
Posted by haifeng on 2011-04-28 22:35:25
分别就 $n=3k$, $n=3k+1$, $n=3k+2$ 讨论即可.
