3870. Count Commas in Range

You are given an integer n. Return the total number of commas used when writing all integers from [1, n] (inclusive) in standard number formatting. In standard formatting: - A comma is inserted after every three digits from the right. - Numbers with fewer than 4 digits contain no commas. Example 1: Input: n = 1002 Output: 3 Explanation: The numbers "1,000", "1,001", and "1,002" each con