# 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).

# 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.

class Solution:
    def maximum69Number (self, num: int) -> int:
        new = list(str(num))
        for i in range(len(new)):
            if new[i] == "6":
                new[i] = "9"
                break
        return ''.join(new)
        
        
 # oneliner
 #      return int(str(num).replace('6', '9', 1))
