You are given two integers, num and k.

Determine the minimum possible size of a collection of positive integers where each integer has a units digit equal to k, and the sum of all integers in the collection equals num.

Return the minimum size of such a collection, or $-1$ if no valid collection exists.

Note: The sum of an empty collection is considered $0$. The collection may contain multiple instances of the same integer.

Constraints:

• $0 \leq$ num $\leq 3000$

• $0 \leq$ k $\leq 9$

Now, let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Implement your solution in the following coding playground.