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Given a positive integer `num`

consisting only of digits 6 and 9.

Return the maximum number you can get by changing **at most** one digit
(6 becomes 9, and 9 becomes 6).

**Example 1:**

Input:num = 9669Output:9969Explanation:Changing the first digit results in 6669. Changing the second digit results in 9969. Changing the third digit results in 9699. Changing the fourth digit results in 9666. The maximum number is 9969.

**Example 2:**

Input:num = 9996Output:9999Explanation:Changing the last digit 6 to 9 results in the maximum number.

**Example 3:**

Input:num = 9999Output:9999Explanation:It is better not to apply any change.

**Constraints:**

`1 <= num <= 10^4`

`num`

's digits are 6 or 9.

All contents and pictures on this website come from the Internet and are updated regularly every week. They are for personal study and research only, and should not be used for commercial purposes. Thank you for your cooperation.