1399. Count Largest Group

You are given an integer n. We need to group the numbers from 1 to n according to the sum of its digits. For example, the numbers 14 and 5 belong to the same group, whereas 13 and 3 belong to different groups. Return the number of groups that have the largest size, i.e. the maximum number of elements. Example 1: Input: n = 13 Output: 4 Explanation: There are 9 groups in total, they are group