c# 100%
```public class Solution {\n    public string GreatestLetter(string s) {\n        \n        for (char c = \'Z\'; c >= \'A\'; c--)\n        {\n            if(s.C
```public class Solution {\n    public string GreatestLetter(string s) {\n        \n        for (char c = \'Z\'; c >= \'A\'; c--)\n        {\n            if(s.Contains(c) && s.Contains(char.ToLower(c)))\n            {\n                return c.ToString();\n            }\n        } \n        \n        return "";\n    }\n} \n
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