Given a string letters and a set of words, find the longest word in words that is a subsequence of letters.

Word W is a subsequence of letters if some number of characters, possibly zero, can be deleted from letters to form W, without reordering the remaining characters. If no subsequence can be found, return an empty string.

Example 1:

The words "able" and "ale" are both subsequences of letters, but they are shorter than "apple". The word "bale" is not a subsequence of letters because even though letters has all the right letters, they are not in the right order. The word "kangaroo" is the longest word in words, but it isn't a subsequence of letters.

Example 2:

letters contains some of the characters in each of the words, however it can't complete any of the words, thus no subsequence found.

Example 3:

All of the words are subsequences of letters, the largest being diamond.