Watering Grass

题目描述

[problemUrl]: https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=15&page=show_problem&problem=1323 [PDF](https://uva.onlinejudge.org/external/103/p10382.pdf) ![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA10382/388518f8e3e8ce10ab22098197e19c4149d773e6.png)

输入输出格式

输入格式


![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA10382/043b45f29e67e742e9130267198ea7bfe60d35bf.png)

输出格式


![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA10382/73a7083285137761e2b9ea258ed541ab44ff938d.png)

输入输出样例

输入样例 #1

8 20 2
5 3
4 1
1 2
7 2
10 2
13 3
16 2
19 4
3 10 1
3 5
9 3
6 1
3 10 1
5 3
1 1
9 1

输出样例 #1

6
2
-1