Transform to Palindrome?

You are given a string s that consists of lowercase letters and the character '?'. The task is to determine whether it is possible to replace each occurrence of '?' with a lowercase letter such that the resulting string is a palindrome.

A string is a palindrome if it reads the same forward and backward. Formally, for a string of length n, it must satisfy the condition $$s_i = s_{n-i-1}\quad \text{for all } 0 \le i < \frac{n}{2}.$$

If for every position i in the first half of the string, either s[i] == s[n-i-1] or at least one of them is '?', then it is always possible to choose appropriate letters to form a palindrome. Otherwise, if there exists an index i such that both characters are fixed and not equal, then the answer is "NO".

Print YES if it is possible to form a palindrome, otherwise print NO.

inputFormat

The input consists of a single line containing the string s with length between 1 and 10⁵. The string contains only lowercase letters and the character '?'.

outputFormat

Output a single line with either YES if the string can be transformed into a palindrome, or NO otherwise.

a?c?c?a

YES