2180\. Count Integers With Even Digit Sum

Easy

Given a positive integer `num`, return _the number of positive integers **less than or equal to**_ `num` _whose digit sums are **even**_.

The **digit sum** of a positive integer is the sum of all its digits.

**Example 1:**

**Input:** num = 4

**Output:** 2

**Explanation:** 

The only integers less than or equal to 4 whose digit sums are even are 2 and 4.

**Example 2:**

**Input:** num = 30

**Output:** 14

**Explanation:** 

The 14 integers less than or equal to 30 whose digit sums are even are 

2, 4, 6, 8, 11, 13, 15, 17, 19, 20, 22, 24, 26, and 28.

**Constraints:**

* `1 <= num <= 1000`
