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 = 555 Output: 888 Explanation: 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 = 9 Output: 8 Explanation: 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 = 123456 Output: 820000 Example 4: Input: num = 10000 Output: 80000 Example 5: Input: num = 9288 Output: 8700 Constraints: 1 <= num <= 10^8