9582: ABC243 —— F - Lottery
Description
Each time he takes a draw, he gets one of the $N$ prizes available. Prize $i$ is awarded with probability $\frac{W_i}{\sum_{j=1}^{N}W_j}$. The results of the draws are independent of each other.
What is the probability that he gets exactly $M$ different prizes from $K$ draws? Find it modulo $998244353$.
Note
To print a rational number, start by representing it as a fraction $\frac{y}{x}$. Here, $x$ and $y$ should be integers, and $x$ should not be divisible by $998244353$ (under the Constraints of this problem, such a representation is always possible). Then, print the only integer $z$ between $0$ and $998244352$ (inclusive) such that $xz\equiv y \pmod{998244353}$.
Input
```
$N$ $M$ $K$
$W_1$
$\vdots$
$W_N$
```
Output
Constraints
- $1 \leq M \leq N \leq 50$
- $0 < W_i$
- $0 < W_1 + \ldots + W_N < 998244353$
- All values in input are integers.
Sample 1 Input
2 1 2
2
1
Sample 1 Output
221832079
Each draw awards Prize 1 with probability $\frac{2}{3}$ and Prize 2 with probability $\frac{1}{3}$.
He gets Prize 1 at both of the two draws with probability $\frac{4}{9}$, and Prize 2 at both draws with probability $\frac{1}{9}$, so the sought probability is $\frac{5}{9}$.
The modulo 998244353 representation of this value, according to Note, is 221832079221832079.
Sample 2 Input
3 3 2
1
1
1
Sample 2 Output
0
Sample 3 Input
3 3 10
499122176
499122175
1
Sample 3 Output
335346748
10 8 15
1
1
1
1
1
1
1
1
1
1
755239064