201345: [AtCoder]ARC134 F - Flipping Coins

Problem Statement

There are $N$ coins numbered $1, 2, \ldots, N$ arranged in a row. Initially, all coins face up.

Snuke chooses a permutation $p$ of $(1,\ldots,N)$ with equal probability, and do $N$ operations. The $i$-th operation does the following.

• If the coin numbered $i$ faces down, do nothing.
• If the coin numbered $i$ faces up, turn that coin over and then turn over the coin numbered $p_i$.

After the $N$ operations, Snuke will receive $W^k$ yen (Japanese currency) from his mother, where $k$ is the number of coins facing up.

Find the expected value of the amount Snuke will get, multiplied by $N!$ (it can be proved that this is an integer), modulo $998244353$.

Constraints

• All values in input are integers.
• $1 \leq N \leq 2 \times 10^5$
• $1 \leq W < 998244353$

Input

Input is given from Standard Input in the following format:

$N$ $W$ 

Output

Print the expected value of the amount Snuke will get, multiplied by $N!$, modulo $998244353$.

Sample Input 1

4 2

Sample Output 1

90

• When $p=(1,4,2,3)$, the operations go as follows.
  • In the $1$-st operation, the coin numbered $1$ faces down, and then the coin numbered $1$ faces up.
  • In the $2$-nd operation, the coin numbered $2$ faces down, and then the coin numbered $4$ faces down.
  • In the $3$-rd operation, the coin numbered $3$ faces down, and then the coin numbered $2$ faces up.
  • In the $4$-th operation, nothing is done.
• In the end, two coins face up, so he receives $4$ yen.

Sample Input 2

2 100

Sample Output 2

10001

Sample Input 3

200000 12345

Sample Output 3

541410753

• Be sure to find the value modulo $998244353$.