Count Sequences

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Points: 0.10
Time limit: 4.0s
Memory limit: 1G

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Problem type
Problem Statement

Find the number of sequences of integers with ~N~ terms, ~A=(a_1,a_2,\ldots,a_N)~ , that satisfy the following conditions, modulo ~998244353~ .

  • ~0 \leq a_1 \leq a_2 \leq \ldots \leq a_N \leq M~ .
  • For each ~i=1,2,\ldots,N-1~ , the remainder when ~a_i~ is divided by ~3~ is different from the remainder when ~a_{i+1}~ is divided by ~3~ .
Constraints
  • ~2 \leq N \leq 10^7~
  • ~1 \leq M \leq 10^7~
  • All values in the input are integers.

Input

The input is given from Standard Input in the following format:

~N~ ~M~

Output

Print the answer.


Sample Input 1
3 4
Sample Output 1
8

Here are the eight sequences that satisfy the conditions.

  • ~(0,1,2)~
  • ~(0,1,3)~
  • ~(0,2,3)~
  • ~(0,2,4)~
  • ~(1,2,3)~
  • ~(1,2,4)~
  • ~(1,3,4)~
  • ~(2,3,4)~

Sample Input 2
276 10000000
Sample Output 2
909213205

Be sure to find the count modulo ~998244353~ .


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