Greatest English Letter in Upper and Lower Case
```class Solution:\n    def greatestLetter(self, s: str) -> str:\n        l=[]\n        m=[]\n        for i in s:\n            l.append(i)\n        for i in l:\
```class Solution:\n    def greatestLetter(self, s: str) -> str:\n        l=[]\n        m=[]\n        for i in s:\n            l.append(i)\n        for i in l:\n            c=ord(i)\n            if (chr(c+32) or chr(c-32)) in l:\n                m.append(chr(c))\n        if len(m)!=0:\n            return max(m)\n        else:\n            return ""\n        \'\'\'
['Python3']