You are given an integer `num`

. You will apply the following steps exactly **two** times:

- Pick a digit
`x (0 <= x <= 9)`

. - Pick another digit
`y (0 <= y <= 9)`

. The digit`y`

can be equal to`x`

. - Replace all the occurrences of
`x`

in the decimal representation of`num`

by`y`

. - The new integer
**cannot**have any leading zeros, also the new integer**cannot**be 0.

Let `a`

and `b`

be the results of applying the operations to `num`

the first and second times, respectively.

Return *the max difference* between `a`

and `b`

.

**Example 1:**

Input:num = 555Output:888Explanation:The first time pick x = 5 and y = 9 and store the new integer in a. The second time pick x = 5 and y = 1 and store the new integer in b. We have now a = 999 and b = 111 and max difference = 888

**Example 2:**

Input:num = 9Output:8Explanation:The first time pick x = 9 and y = 9 and store the new integer in a. The second time pick x = 9 and y = 1 and store the new integer in b. We have now a = 9 and b = 1 and max difference = 8

**Example 3:**

Input:num = 123456Output:820000

**Example 4:**

Input:num = 10000Output:80000

**Example 5:**

Input:num = 9288Output:8700

**Constraints:**

`1 <= num <= 10^8`

class Solution:
def maxDiff(self, num: int) -> int: