Have the function ProductDigits(num) take the num parameter being passed
which will be a positive integer, and determine the least amount of digits you
need to multiply to produce it. For example: if num is 24 then
you can multiply 8 by 3 which produces 24, so your program should return 2 because
there is a total of only 2 digits that are needed. Another example: if num is 90, you can multiply
10 * 9, so in this case your program should output 3 because
you cannot reach 90 without using a total of 3 digits in your multiplication.
Examples
Input: 6
Output: 2
Input: 23
Output: 3