请求撤下部分题解，原因为本题虽然一眼可以看出结论，但是希望可以列出推导过程，而不是直接说“一眼看出来”，那这样的题解似乎没有意义：

• https://www.luogu.com.cn/article/j4xxq9k3
• https://www.luogu.com.cn/article/ufg38754
• https://www.luogu.com.cn/article/jcfbkwp5
• https://www.luogu.com.cn/article/6jjpik56
• https://www.luogu.com.cn/article/0bixha3j
• https://www.luogu.com.cn/article/6b9zch0w
• https://www.luogu.com.cn/article/21yee32e
• https://www.luogu.com.cn/article/r51p3lb6
• https://www.luogu.com.cn/article/gsjz09k5
• https://www.luogu.com.cn/article/6b4upyfd
• https://www.luogu.com.cn/article/uiift7ox
• https://www.luogu.com.cn/article/w4tpnyaj
• https://www.luogu.com.cn/article/06bnwecl
• https://www.luogu.com.cn/article/7fx7on5r
• https://www.luogu.com.cn/article/dhiie0l0