Python3| Easy Understand
```python\n        global_max = ""\n        curr_max = ""\n        for char in s:\n          if char.swapcase() in s:\n            curr_max = char.upper()\n    
```python\n        global_max = ""\n        curr_max = ""\n        for char in s:\n          if char.swapcase() in s:\n            curr_max = char.upper()\n          global_max = max(curr_max,global_max)\n        return global_max\n
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