后来居然卡了一道2-sat，原来是将n写成了m,小错误总是不停的犯，也该到头了吧～
6道2-sat题号
> POJ 3207 - Ikki's Story IV - Panda's Trick
> http://acm.pku.edu.cn/JudgeOnline/problem?id=3207
> POJ 3678 - Katu Puzzle
> http://acm.pku.edu.cn/JudgeOnline/problem?id=3678
> POJ 2723 - Get Luffy Out
> http://acm.pku.edu.cn/JudgeOnline/problem?id=2723
> POJ 3683 - Priest John's Busiest Day
> http://acm.pku.edu.cn/JudgeOnline/problem?id=3683
> POJ 2749 - Building roads
> http://acm.pku.edu.cn/JudgeOnline/problem?id=2749
> POJ 3648- Wedding
> http://acm.pku.edu.cn/JudgeOnline/problem?id=3648