
Given a list of words , list of single letters (might be repeating) and score of every character.
Return the maximum score of any valid set of words formed by using the given letters ( words[i] cannot be used two or more times).
It is not necessary to use all characters in letters and each letter can only be used once. Score of letters 'a' , 'b' , 'c' , ... , 'z' is given by score[0] , score[1] , ... , score[25] respectively.
1 <= words.length <= 141 <= words[i].length <= 151 <= letters.length <= 100letters[i].length == 1score.length == 260 <= score[i] <= 10words[i] , letters[i] contains only lower case English letters.