Return the length of the longest contiguous substring of s in which each vowel (a, e, i, o, and u) occurs an even number of times. Zero occurrences is even. Consonants have no restrictions.
Example 1:
Input: s = "aaeb"
Output: 2Explanation: The substring "aa" has two occurrences of a and zero of every other vowel, giving length 2. Every longer substring contains the lone e an odd number of times.
Example 2:
Input: s = "bcdf"
Output: 4Explanation: The whole string has zero occurrences of every vowel. Zero is even, so all four characters qualify.
Example 3:
Input: s = "aeiouaeiou"
Output: 10Explanation: The entire string contains each vowel exactly twice, so its full length of 10 qualifies.
Constraints:
1 <= s.length <= 500000- Only lowercase English letters occur.