http://acm.tzc.edu.cn/acmhome/problemdetail.do?&method=showdetail&id=4453
不会
http://acm.tzc.edu.cn/acmhome/problemdetail.do?&method=showdetail&id=4454
理论AC
http://acm.tzc.edu.cn/acmhome/problemdetail.do?&method=showdetail&id=4471
理论AC
原文：http://blog.csdn.net/u011686226/article/details/45584999