Problem9616--ABC247 —— Ex - Rearranging Problem

9616: ABC247 —— Ex - Rearranging Problem

[Creator : ]
Time Limit : 2.000 sec  Memory Limit : 512 MiB

Description

There are $N$ people called Person $1$, Person $2$, $\dots$, Person $N$, lined up in a row in the order of $(1,2,\dots,N)$ from the front. Person $i$ is wearing Color $c_i$.  
Takahashi repeated the following operation $K$ times: choose two People $i$ and $j$ arbitrarily and swap the positions of Person $i$ and Person $j$.  
After the $K$ operations have ended, the color that the $i$-th person from the front is wearing coincided with $c_i$, for every integer $i$ such that $1 \leq i \leq N$.  
How many possible permutations of people after the $K$ operations are there? Find the count modulo $998244353$.

Input

Input is given from Standard Input in the following format:

```
$N$ $K$
$c_1$ $c_2$ $\dots$ $c_N$
```

Output

Print the answer.

Constraints

-   $2 \leq N \leq 200000$
-   $1 \leq K \leq 10^9$
-   $1 \leq c_i \leq N$
-   All values in input are integers.

Sample 1 Input

4 1
1 1 2 1

Sample 1 Output

3
Here is a comprehensive list of possible Takahashi's operations and permutations of people after each operation.
  • Swap the positions of Person 1 and Person 2, resulting in a permutation (2,1,3,4).
  • Swap the positions of Person 1 and Person 4, resulting in a permutation (4,2,3,1).
  • Swap the positions of Person 2 and Person 4, resulting in a permutation (1,4,3,2).

Sample 2 Input

3 3
1 1 2

Sample 2 Output

1
Here is an example of a possible sequence of Takahashi's operations.
  • In the 1-st operation, he swaps the positions of Person 1 and Person 3, resulting in a permutation (3,2,1).
    In the 2-nd operation, he swaps the positions of Person 2 and Person 3, resulting in a permutation (2,3,1).
    In the 3-rd operation, he swaps the positions of Person 1 and Person 3, resulting in a permutation (2,1,3).
Note that, during the sequence of operations, the color that the i-th person from the front is wearing does not necessarily coincide with $c_i$.

Sample 3 Input

10 4
2 7 1 8 2 8 1 8 2 8

Sample 3 Output

132

Source/Category