Given an array of strings arr. String s is a concatenation of a sub-sequence of arr which have unique characters. Return the maximum possible length of s. Example 1: Input: arr = ["un","iq","ue"] Output: 4 Explanation: All possible concatenations are "","un","iq","ue","uniq" and "ique". Maximum length is 4. Example 2: Input: arr = ["cha","r","act","ers"] Output: 6 Explanation: Possible solutions are "chaers" and "acters". Example 3: Input: arr = ["abcdefghijklmnopqrstuvwxyz"] Output: 26 Constraints: 1 <= arr.length <= 16 1 <= arr[i].length <= 26 arr[i] contains only lower case English letters.