Score : 800 points
Given is a positive even number N.
Find the number of strings s of length N consisting of A, B, and C that satisfy the following condition:
AB or BA is not allowed.For example, ABBC satisfies the condition for N=4, because we can convert it as follows: ABBC → (erase BB) → AC → (erase AC) → (empty).
The answer can be enormous, so compute the count modulo 998244353.
Input is given from Standard Input in the following format:
N
Print the number of strings that satisfy the conditions, modulo 998244353.
2
7
Except AB and BA, all possible strings satisfy the conditions.
10
50007
1000000
210055358