题目描述
Problem Statement
You are given an integer $N. On an integer sequence A = (1, 2, \ldots, N)$, let us do the operation below exactly K times.
- Let n be the current number of terms in A. For all i such that $1\leq i \leq n$ and $i\equiv 1\pmod{3},$ delete the i-th term of A, simultaneously.
Find the sum of the terms of A after K operations, modulo 998244353.
Input
Input is given from Standard Input from the following format:
N K
Output
Print the sum of the terms of A after K operations, modulo 998244353.
Constraints
- $1\leq N\leq 10^{14}$
- $1\leq K\leq 100$
Sample Input 1
10 2
Sample Output 1
25
- Initially, we have A = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10).
- After the first operation, we have A = (2, 3, 5, 6, 8, 9).
- After the second operation, we have A = (3, 5, 8, 9).
- The sum of the terms here is 3 + 5 + 8 + 9 = 25.
Sample Input 2
10 10
Sample Output 2
0
- After the second operation, we have A = (3, 5, 8, 9) (same as Sample Input 1).
- After the third operation, we have A = (5, 8).
- After the fourth operation, we have A = (8).
- After the fifth operation, A is empty.
- In the sixth and subsequent operations, A remains empty, where the sum of the terms is 0.
Sample Input 3
10000 10
Sample Output 3
862816
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分
样例输入
10 2
样例输出
25