题目描述
Problem Description
Given a random permutation of length $n$, find the expected length of its longest increasing subsequence.
To avoid precision errors, you only need to output the remainder of the answer modulo $998244353$.
Input Format
The input consists of a single positive integer $n$.
Output Format
The output consists of a single non-negative integer, which is the remainder of the answer modulo $998244353$.
It can be proven that the answer is always a rational number, denoted as $a/b$ (where $a$ and $b$ are coprime integers). Let $x$ be the integer you output, then you need to ensure that $0 \le x < 998244353$ and $a$ is congruent to $b \cdot x$ modulo $998244353$.
Sample Input and Output
Sample Input #1
1
Sample Output #1
1
Sample Input #2
2
Sample Output #2
499122178
Sample Input #3
3
Sample Output #3
2
Notes
[Sample #2 Explanation]
This corresponds to $3/2$.
[Data Range and Constraints]
For $100\%$ of the data, $1 \le n \le 28$.
There are 25 sets of data. For the $i$-th set of data ($1 \le i \le 25$), $n = i + 3$.
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分