UVA10919 Prerequisites?

Description

[problemUrl]: https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=21&page=show_problem&problem=1860 [PDF](https://uva.onlinejudge.org/external/109/p10919.pdf) ![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA10919/a32e7c769803047479d0629702568671e90d92df.png)

Input Format

![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA10919/129e9c8f00b38ddbea98428fae5fde7a85bda48a.png)

Output Format

![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA10919/954aeee46e40d809c97c2765e204330d2042751c.png)