Python 1-liner
The intersection between the uppercase and lowercase string results the characters of interest.\n\n\nclass Solution:\n    def greatestLetter(self, s: str) -> st
The intersection between the uppercase and lowercase string results the characters of interest.\n\n```\nclass Solution:\n    def greatestLetter(self, s: str) -> str:\n        return max(Counter(s) & Counter(s.swapcase()), default="").upper()\n```
['Python', 'Python3']