容斥原理

题目：hdu 1796, hdu 1685,hdu 2204,hdu 4407 ,hdu 2841

http://acm.swust.edu.cn/oj/problem/821/

http://zuojie.3322.org:88/soj/problem.action?id=3137

http://acm.hdu.edu.cn/showproblem.php?pid=1796

http://acm.hdu.edu.cn/showproblem.php?pid=1695

http://poj.org/problem?id=3904

hdu 2841

http://yzmduncan.iteye.com/blog/1315175

http://www.cnblogs.com/scau20110726/archive/2013/03/18/2966089.html

http://www.byywee.com/page/M0/S848/848250.html

http://www.cppblog.com/vici/archive/2011/09/05/155103.html