题目描述
Problem Statement
You have an integer 1 and a die that shows integers between 1 and 6 (inclusive) with equal probability.
You repeat the following operation while your integer is strictly less than N:
- Cast a die. If it shows x, multiply your integer by x.
Find the probability, modulo 998244353, that your integer ends up being N.
How to find a probability modulo 998244353?
We can prove that the sought probability is always rational.
Additionally, under the constraints of this problem, when that value is represented as $\frac{P}{Q}$ with two coprime integers P and Q, we can prove that there is a unique integer R such that $R \times Q \equiv P\pmod{998244353}$ and $0 \leq R \lt 998244353.$ Find this R.
Input
The input is given from Standard Input in the following format:
N
Output
Print the probability, modulo 998244353, that your integer ends up being N.
Constraints
- $2 \leq N \leq 10^{18}$
- N is an integer.
Sample Input 1
6
Sample Output 1
239578645
One of the possible procedures is as follows.
- Initially, your integer is 1.
- You cast a die, and it shows $2. Your integer becomes 1 \times 2 = 2$.
- You cast a die, and it shows $4. Your integer becomes 2 \times 4 = 8$.
- Now your integer is not less than 6, so you terminate the procedure.
Your integer ends up being 8, which is not equal to N = 6.
The probability that your integer ends up being 6 is $\frac{7}{25}. Since 239578645 \times 25 \equiv 7 \pmod{998244353}$, print 239578645.
Sample Input 2
7
Sample Output 2
0
No matter what the die shows, your integer never ends up being 7.
Sample Input 3
300
Sample Output 3
183676961
Sample Input 4
979552051200000000
Sample Output 4
812376310
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分