simple solution - python
\nclass Solution:\n    def modifyString(self, s: str) -> str:\n        res = list(s)\n        \n        for i in range(len(res)):\n            if res[i] == \'?\
```\nclass Solution:\n    def modifyString(self, s: str) -> str:\n        res = list(s)\n        \n        for i in range(len(res)):\n            if res[i] == \'?\':\n                left = res[i-1] if i > 0 else \'\'\n                right = res[i+1] if i < len(s) - 1 else \'\'\n                \n                for ch in \'abc\':\n                    if ch != left and ch != right:\n                        res[i] = ch\n                        break\n        \n        return \'\'.join(res)\n```
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