$ cat ./coding/1323-maximum-69-number.md

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1323. Maximum 69 Number

class Solution:
    def maximum69Number (self, num: int) -> int:
        
        s = str(num)
        
        res = []
        
        count = 1
        for i in range(len(s)):
            if s[i] == '9':
                res.append(s[i])
            else:
                if count == 1:
                    res.append('9')
                    count -= 1
                else:
                    res.append(s[i])
        
        return int(''.join(res))

$ ls ./coding/ | grep -v 1323-maximum-69-number