Palindrome Permutation

Given a string s, determine whether its characters can be rearranged to form a palindrome. A string can be rearranged into a palindrome if and only if at most one character appears an odd number of times. Mathematically, this condition can be expressed as:

$$\sum_{c \in \Sigma} \bigl[\text{count}(c) \bmod 2 \neq 0\bigr] \leq 1$$

For example, the string "aaabbbb" can be rearranged to form a palindrome (e.g., "bbaaabb"), whereas "cdefghmnopqrstuvw" cannot.

inputFormat

The input consists of a single line containing a non-empty string s of lowercase letters.

outputFormat

Output a single line with the string YES if the input string can be rearranged to form a palindrome, and NO otherwise.

aaabbbb

YES