Kata

Some numbers can be expressed as a difference of two squares, for example, 20 = 62-42 and 21 = 52-22. Many numbers can be written this way, but not all.

Your Task

Complete the function that takes a positive integer n and returns the amount of numbers between 1 and n (inclusive) that can be represented as the difference of two perfect squares.

Note: Your code should be able to handle n values up to 45000

Examples

n = 4 ==> 3
n = 5 ==> 4
n = 10 ==> 7
n = 20 ==> 15
n = 6427 ==> 4820