UVA11631 Dark roads

Description

[problemUrl]: https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=78&page=show_problem&problem=2678 [PDF](https://uva.onlinejudge.org/external/116/p11631.pdf) ![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA11631/3b6d8ed066db76a33df958a6c0c60e1de6f08826.png)

Input Format

![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA11631/7734ca5ac043999aba0dd88070cb0666c4ceb068.png)

Output Format

![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA11631/1ed1cc0f3f59d366bbd1502cdf64865f590a4679.png)