input
1 abcdefghijklmnopqrstuvwxyzaabcdefghijklmnopqrstuvwxyz
output
677
被 hack 的题解:
https://www.luogu.com.cn/blog/0123456-3456789/solution-p7114
https://www.luogu.com.cn/blog/daniu/solution-p7114
https://www.luogu.com.cn/blog/1-2-1/solution-p7114
https://www.luogu.com.cn/blog/cjtcalc/solution-p7114(算法二)
https://www.luogu.com.cn/blog/lhc-yyl-lyx-lyh/solution-p7114(前三份代码)
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