Given an integer n. Each number from 1 to n is grouped according to the sum of its digits. Return how many groups have the largest size. Example 1: Input: n = 13 Output: 4 Explanation: There are 9 groups in total, they are grouped according sum of its digits of numbers from 1 to 13: [1,10], [2,11], [3,12], [4,13], [5], [6], [7], [8], [9]. There are 4 groups with largest size. Example 2: Input: n = 2 Output: 2 Explanation: There are 2 groups [1], [2] of size 1. Example 3: Input: n = 15 Output: 6 Example 4: Input: n = 24 Output: 5 Constraints: 1 <= n <= 10^4