Given two strings a and b, return the length of the longest uncommon subsequence between a and b. If no such uncommon subsequence exists, return -1.
An uncommon subsequence between two strings is a string that is a subsequence of exactly one of them.
Example 1:
Input: a = "aba", b = "cdc" Output: 3 Explanation: One longest uncommon subsequence is "aba" because "aba" is a subsequence of "aba" but not "cdc". Note that "cdc" is also a longest uncommon subsequence.
Example 2:
Input: a = "aaa", b = "bbb" Output: 3 Explanation: The longest uncommon subsequences are "aaa" and "bbb".
Example 3:
Input: a = "aaa", b = "aaa"
Output: -1
Explanation: Every subsequence of string a is also a subsequence of string b. Similarly, every subsequence of string b is also a subsequence of string a. So the answer would be -1.
Constraints:
1 <= a.length, b.length <= 100a and b consist of lower-case English letters."aba" "cdc" "aaa" "bbb" "aaa" "aaa"