Mayor's posters

题目描述

[problemUrl]: https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=17&page=show_problem&problem=1528 [PDF](https://uva.onlinejudge.org/external/105/p10587.pdf) ![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA10587/cd78d581a1fc6c9ec2d9b3173f9b68a09424475e.png)

输入输出格式

输入格式


![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA10587/6436da42b41ec1428b97672792b9d28ec339a310.png)

输出格式


![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA10587/6242da124237600afd35badbcef3a1cefd8b37f9.png)

输入输出样例

输入样例 #1

1
5
1 4
2 6
8 10
3 4
7 10

输出样例 #1

4