2243. Calculate Digit Sum of a String

You are given a string s consisting of digits and an integer k. A round can be completed if the length of s is greater than k. In one round, do the following: - Divide s into consecutive groups of size k such that the first k characters are in the first group, the next k characters are in the second group, and so on. Note that the size of the last group can be smaller than k. - Replace each gro