simple-eviternity-numbers

Simple eviternity numbers

An eviternity number is a number which:

• contains only digits 8, 5 and 3, and
• the count of the digit 8 >= count of digit 5 >= count of digit 3.

The first few eviternity numbers are as follows.

[8, 58, 85, 88, 358, 385, 538, 583, 588, 835, 853, 858, 885, 888]

You will be given two integers, a and b, and your task is to return the number of eviternity numbers in the range >= a and < b.

For example:
solve(0,1000) = 14, because they are [8, 58, 85, 88, 358, 385, 538, 583, 588, 835, 853, 858, 885, 888]

The upper bound will not exceed 500,000.