Given a string s and an integer k, construct a new string by keeping only the characters whose total frequency in s is strictly less than k. The relative order of the remaining characters must be preserved.

Return the filtered string.

Constraints:

• $1 \leq$ s.length $\leq 100$

• s consists of lowercase English letters.

• $1 \leq$ k $\leq$ s.length

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.