Ouroboros Snake

题目描述

[problemUrl]: https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=12&page=show_problem&problem=981 [PDF](https://uva.onlinejudge.org/external/100/p10040.pdf) ![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA10040/44b0556fdf2d441617c1bec0badb238a503fc7ff.png)

输入输出格式

输入格式


![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA10040/9eb81f54090c35454eaa362a3f071ae3809c0410.png)

输出格式


![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA10040/9b825da1a85f42198f657cc64b4cffb15b63fd42.png)

输入输出样例

输入样例 #1

4
2 0
2 1
2 2
2 3

输出样例 #1

0
1
3
2