输入：

1
1
0

应输出：0

https://www.luogu.com.cn/blog/MorikuraAme/solution-cf510d: -1

https://www.luogu.com.cn/blog/GDX/cf510d-ti-xie: -1

https://www.luogu.com.cn/blog/s19418/solution-cf510d: -1

https://www.luogu.com.cn/blog/A-happy-shit/solution-cf510d: -1