# ---
# title: 1323. Maximum 69 Number
# id: problem1323
# author: Tian Jun
# date: 2020-10-31
# difficulty: Easy
# categories: Math
# link: <https://leetcode.com/problems/maximum-69-number/description/>
# hidden: true
# ---
# 
# 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 = 9669
#     Output: 9969
#     Explanation: 
#     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 = 9996
#     Output: 9999
#     Explanation: Changing the last digit 6 to 9 results in the maximum number.
# 
# **Example 3:**
# 
#     
#     
#     Input: num = 9999
#     Output: 9999
#     Explanation: It is better not to apply any change.
# 
# 
# 
# **Constraints:**
# 
#   * `1 <= num <= 10^4`
#   * `num`'s digits are 6 or 9.
# 
# 
## @lc code=start
using LeetCode

## add your code here:
## @lc code=end
