Score : $600$ points
There are $N$ chairs arranged in a row, called Chair $1$, Chair $2$, $\ldots$, Chair $N$.
A chair seats only one person.
$M$ people will sit on $M$ of these chairs. Here, let us define the score as follows:
$\displaystyle \prod_{i=1}^{M-1} (B_{i+1} - B_i)$, where $B=(B_1,B_2,\ldots,B_M)$ is the sorted list of the indices of the chairs the people sit on.
Person $i$ $(1 \leq i \leq K)$ is already sitting on Chair $A_i$.
There are ${} _ {N-K} \mathrm{P} _ {M-K}$ ways for the other $M-K$ people to take seats. Find the sum of the scores for all of these ways.
Since this sum may be enormous, compute it modulo $998244353$.
Input is given from Standard Input in the following format:
$N$ $M$ $K$ $A_1$ $A_2$ $\ldots$ $A_K$
Print the answer.
5 3 2 1 3
7
If Person $3$ sits on Chair $2$, the score will be $(2-1) \times (3-2)=1 \times 1 = 1$.
If Person $3$ sits on Chair $4$, the score will be $(3-1) \times (4-3)=2 \times 1 = 2$.
If Person $3$ sits on Chair $5$, the score will be $(3-1) \times (5-3)=2 \times 2 = 4$.
The answer is $1+2+4=7$.
6 6 1 4
120
The score for every way of sitting will be $1$.
There are ${} _ {5} \mathrm{P} _ {5} = 120$ ways of sitting, so the answer is $120$.
99 10 3 10 50 90
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