题目描述
We have $3N$ colored balls with IDs from $1$ to $3N$. A string $S$ of length $3N$ represents the colors of the balls. The color of Ball $i$ is red if $S_i$ is `R`, green if $S_i$ is `G`, and blue if $S_i$ is `B`. There are $N$ red balls, $N$ green balls, and $N$ blue balls.
Takahashi will distribute these $3N$ balls to $N$ people so that each person gets one red ball, one blue ball, and one green ball. The people want balls with IDs close to each other, so he will additionally satisfy the following condition:
- Let $a_j < b_j < c_j$ be the IDs of the balls received by the $j$\-th person in ascending order.
- Then, $\sum_j (c_j-a_j)$ should be as small as possible.
Find the number of ways in which Takahashi can distribute the balls. Since the answer can be enormous, compute it modulo $998244353$. We consider two ways to distribute the balls different if and only if there is a person who receives different sets of balls.
输入格式
Input is given from Standard Input in the following format:
>$N$\
>$S$
#### Constraints
- $1 \leq N \leq 10^5$
- $|S|=3N$
- $S$ consists of `R`, `G`, and `B`, and each of these characters occurs $N$ times in $S$.
输出格式
Print the number of ways in which Takahashi can distribute the balls, modulo $998244353$.
样例输入 #1
3 RRRGGGBBB
样例输出 #1
216
样例输入 #2
5 BBRGRRGRGGRBBGB
样例输出 #2
960
提示
***For Sample #1:***
The minimum value of $\sum_j (c_j-a_j)$ is $18$ when the balls are, for example, distributed as follows:
- The first person gets Ball $1$, $5$, and $9$.
- The second person gets Ball $2$, $4$, and $8$.
- The third person gets Ball $3$, $6$, and $7$.