Given an integer number `n`, return the difference between the product of its digits and the sum of its digits.

Example 1:

    Input: n = 234
    Output: 15
    Explanation:
    Product of digits = 2 * 3 * 4 = 24
    Sum of digits = 2 + 3 + 4 = 9
    Result = 24 - 9 = 15

Example 2:

    Input: n = 4421
    Output: 21
    Explanation:
    Product of digits = 4 * 4 * 2 * 1 = 32
    Sum of digits = 4 + 4 + 2 + 1 = 11
    Result = 32 - 11 = 21

Constraints:

- `1 <= n <= 10^5`