Freckles

题目描述

[problemUrl]: https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=12&page=show_problem&problem=975 [PDF](https://uva.onlinejudge.org/external/100/p10034.pdf) ![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA10034/b178fe12ab2684d531a2d302e9fc9c585ba1f680.png)

输入输出格式

输入格式


![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA10034/638a354ad459c082b972d9ad33cc8fce903e7399.png)

输出格式


![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA10034/5d75816129b6b4e6aa59135397a8bbaf14fd87c7.png)

输入输出样例

输入样例 #1

1
3
1.0 1.0
2.0 2.0
2.0 4.0

输出样例 #1

3.41