Valid Palindrome Checker

This problem requires you to determine whether a string is a valid palindrome or not. To check, you must ignore all non-alphanumeric characters and consider only letters and numbers, treating uppercase and lowercase letters as equivalent.

A palindrome is a string that reads the same backward as forward after the non-alphanumeric characters have been removed and the case has been normalized. For example, the string A man, a plan, a canal: Panama becomes a palindrome once processed.

The underlying mathematical idea can be expressed as: $$ \text{Let } s' = \{ c \in s \mid c \text{ is alphanumeric and normalized to lower case} \}. \; \text{Then } s' \text{ is a palindrome if } s' = (s')^R. $$

inputFormat

The input consists of a single string s (which may include spaces, punctuation, or other symbols) provided through stdin.

outputFormat

Output a single line containing YES if the string is a valid palindrome after processing, or NO otherwise. The output should be printed to stdout.

A man, a plan, a canal: Panama

YES