7013: ABC171 —— F - Strivore
[Creator : ]
Description
How many strings can be obtained by applying the following operation on a string $S$ exactly $K$ times: "choose one lowercase English letter and insert it somewhere"?
The answer can be enormous, so print it modulo $(10^9+7)$.
The answer can be enormous, so print it modulo $(10^9+7)$.
Input
Input is given from Standard Input in the following format:
$K$
$S$
$K$
$S$
Output
Print the number of strings satisfying the condition, modulo $(10^9+7)$.
Constraints
$K$ is an integer between $1$ and $10^6$ (inclusive).
$S$ is a string of length between $1$ and $10^6$ (inclusive) consisting of lowercase English letters.
$S$ is a string of length between $1$ and $10^6$ (inclusive) consisting of lowercase English letters.
Sample 1 Input
5
oof
Sample 1 Output
575111451
For example, we can obtain proofend, moonwolf, and onionpuf, while we cannot obtain oofsix, oofelevennn, voxafolt, or fooooooo.
Sample 2 Input
37564
whydidyoudesertme
Sample 2 Output
318008117