Problem Statement
Let ~s~ be the concatenation of ~N~ copies of keyence
. Consider deleting zero or more characters from ~s~ and concatenating the remaining characters without changing the order to make a new string ~s^{\prime}~ .
There are ~2^{7N}~ ways to choose the positions at which we delete the characters. Among them, how many make ~s^{\prime}~ equal to ~t~ ? Find the count modulo ~998244353~ .
Constraints
- ~1 \leq N \leq 10^{18}~
- ~1 \leq |t| \leq 2.5 \times 10^5~
- ~t~ is a string consisting of
c
,e
,k
,n
, andy
.
Input
Input is given from Standard Input in the following format:
~N~
~t~
Output
Print the number of ways to choose the positions at which we delete the characters so that ~s^{\prime}~ will be equal to ~t~ , modulo ~998244353~ .
Sample Input 1
2
key
Sample Output 1
6
- We have ~s=~
keyencekeyence
. - There are six ways to choose the positions at which we delete the characters so that ~s^{\prime}=~
key
.
Sample Input 2
2
ccc
Sample Output 2
0
- There are zero ways to choose the positions at which we delete the characters so that ~s^{\prime}=~
ccc
.
Sample Input 3
100
keyneeneeeckyycccckkke
Sample Output 3
275429980
- Be sure to find the count modulo ~998244353~ .
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