Problem Statement

A string $T$ is called a good string when it satisfies the following condition:

• There is a pair of strings $(A, B)$ that satisfies all of the following:
• Both $A$ and $B$ are non-empty.
  • $A + B = T$.
  • Both $A + \mathrm{rev}(B)$ and $\mathrm{rev}(A) + B$ are palindromes.

Here, $A + B$ denotes the string formed by concatenating strings $A$ and $B$ in this order. Also, $\mathrm{rev}(A)$ denotes the string formed by reversing the order of the characters in string $A$.

There is a string $S$ of length $N$ consisting of lowercase English letters and the character ?. Among the $26^{(\text{number of ?s})}$ ways to replace the ?s in $S$ with lowercase English letters, how many result in a good string? Find the count modulo $998244353$.

Constraints

• $2 \leq N \leq 5 \times 10^4$
• $S$ is a string of length $N$ consisting of lowercase English letters and ?.

Input

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

N
S

Output

Print the number, modulo $998244353$, of ways to replace the characters that satisfy the condition in the problem statement.