1399\. Count Largest Group

Easy

You are given an integer `n`.

Each number from `1` to `n` is grouped according to the sum of its digits.

Return _the number of groups that 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.

**Constraints:**

*   <code>1 <= n <= 10<sup>4</sup></code>