Even Frequency Check

Little Blue really likes even numbers. Whenever he sees a string, he wishes to verify that every character in the string appears an even number of times. Given a string, please help Little Blue determine whether the string satisfies this requirement.

Note that every character’s count must be even. If any character appears an odd number of times, the answer is NO; otherwise, the answer is YES.

inputFormat

The input consists of a single line containing a string. The string may contain any printable characters.

outputFormat

Output YES if every character in the string appears an even number of times; otherwise, output NO.

sample

aabb

YES