Easy python solution
\ndef greatestLetter(self, s: str) -> str:\n        c="abcdefghijklmnopqrstuvwxyz"\n        l=[""]\n        for i in c:\n            if i in s and i.upper() in 
```\ndef greatestLetter(self, s: str) -> str:\n        c="abcdefghijklmnopqrstuvwxyz"\n        l=[""]\n        for i in c:\n            if i in s and i.upper() in s:\n                l.append(i.upper())\n        l.sort()\n        return l[-1]\n```
['Python', 'Python3']