Can Form Palindrome?

Given an input string s consisting of only lowercase English letters, determine whether the characters of the string can be rearranged to form a palindrome.

A palindrome is a string that reads the same backward as forward. In order for a string to be rearranged into a palindrome, at most one character can have an odd frequency. This can be expressed mathematically as:

$$\text{Let } odd = \sum_{c \in S} [\text{freq}(c) \bmod 2 \neq 0]. \quad \text{Then, a palindrome is possible if } odd \leq 1.$$

Your task is to output "YES" if the string can be rearranged to form a palindrome, and "NO" otherwise.

inputFormat

The input consists of a single line containing a string s (possibly empty) of lowercase English letters.

outputFormat

Output a single line containing either "YES" if the string can be rearranged into a palindrome, or "NO" if it cannot.

aabb

YES