Hint: maxSize doesn't matter!
If you are able to find substrings with size > minSize  meeting the maxLetters reqirement, substrings with smaller sizes have atleast the same frequency! maxSiz
If you are able to find substrings with ```size > minSize```  meeting the ```maxLetters``` reqirement, substrings with smaller sizes have *atleast* the same frequency! ```maxSize``` is just introduced to cause testcase 40 to fail if you don\'t catch this.
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