Palindrome Checker with Alphanumeric Filter

Given a string \(s\), determine whether it is a palindrome. In this problem, only alphanumeric characters are considered, and case is ignored. That is, let \(s'\) be the string obtained by removing all non-alphanumeric characters from \(s\) and converting the remaining characters to lowercase. The condition for \(s\) to be a palindrome is:

\[ s' = \text{reverse}(s') \]

An empty string is considered a valid palindrome.

inputFormat

The input consists of a single line containing a string \(s\). The string may include spaces, punctuation, and a mix of uppercase and lowercase letters.

outputFormat

Output a single line: "YES" if the string is a palindrome after filtering, or "NO" otherwise.

## sample

A man, a plan, a canal, Panama

YES

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