A solution to last week's challenge can be found here. 
This week's challenge was submitted by @dylan_gao - Thanks for your submission!
"Unity, that is the key word in unit, without the y" -Major Payne
Whether or not you've seen the movie quoted above, odds are good that you have noticed words within words at some point. If you haven't then you've probably never done a word search either....
For this week's challenge, find the longest alphabetically arranged substring within the provided strings. For instance, the string "abcdxyz", the longest substring returns "abcd".
