408247: GYM103069 A Namomo Subsequence

"gshfd1jkhaRaadfglkjerVcvuy0gf" said Prof. Pang.

To understand Prof. Pang's word, we would like to calculate the number of namomo subsequences of it. The word by Prof. Pang is a string $$$s$$$ with $$$n$$$ characters where each character is either an English letter (lower or upper case) or a digit. The $$$i$$$-th character of $$$s$$$ is denoted by $$$s[i]$$$ ($$$1\le i\le n$$$). A subsequence $$$t$$$ of $$$s$$$ is defined by a list of indices $$$t_1, \ldots, t_6$$$ such that $$$1\le t_1 < t_2 < \ldots < t_6\le n$$$. Let $$$compare(c_1, c_2)$$$ be a function on two characters such that $$$compare(c_1, c_2)=1$$$ when $$$c_1=c_2$$$ and $$$compare(c_1, c_2)=0$$$ otherwise. $$$t$$$ is a namomo subsequence of $$$s$$$ if and only if for any $$$1\le i<j\le 6$$$, $$$compare(s[t_i], s[t_j]) = compare(namomo[i], namomo[j])$$$, where $$$namomo[x]$$$ represents the $$$x$$$-th character of the string "namomo" ($$$1\le x\le 6$$$).

Output the number of namomo subsequences of a given string $$$s$$$ modulo $$$998244353$$$.

The first line contains a string $$$s$$$ with $$$n$$$ characters ($$$6\le n\le 1000000$$$). $$$s$$$ contains only lower case English letters ('a' – 'z'), upper case English letters ('A' – 'Z') and digits ('0' – '9').

Output one integer – the answer modulo $$$998244353$$$.

wohaha

1

momomo

0

gshfd1jkhaRaadfglkjerVcvuy0gf

73

retiredMiFaFa0v0

33