F - Strivore

Score: $600$ points

Problem Statement

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 $(10^9+7)$.

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.

Input

Input is given from Standard Input in the following format:

$K$

$S$

Output

Print the number of strings satisfying the condition, modulo $(10^9+7)$.

5
oof

575111451

For example, we can obtain proofend, moonwolf, and onionpuf, while we cannot obtain oofsix, oofelevennn, voxafolt, or fooooooo.

37564
whydidyoudesertme

318008117