Problem:
Score : 300 points

Problem Statement

You are given integers N and K. Find the number of triples (a,b,c) of positive integers not greater than N such that a+b,b+c and c+a are all multiples of K.
The order of a,b,c does matter, and some of them can be the same.

Constraints

1 \leq N,K \leq 2\times 10^5

N and K are integers.

Input

Input is given from Standard Input in the following format:

N K

Output

Print the number of triples (a,b,c) of positive integers not greater than N such that a+b,b+c and c+a are all multiples of K.

Sample Input 1

3 2

Sample Output 1

9

(1,1,1),(1,1,3),(1,3,1),(1,3,3),(2,2,2),(3,1,1),(3,1,3),(3,3,1) and (3,3,3) satisfy the condition.

Sample Input 2

5 3

Sample Output 2

1

Sample Input 3

31415 9265

Sample Output 3

27

Sample Input 4

35897 932

Sample Output 4

114191

Solution in PHP7 (7.0.15) (judge verdict: Wrong Answer)

<?php

	$data = explode(" ", trim(fgets(STDIN)));
	$n = $data[0];
	$k = $data[1];
	
	$x = floor($n/$k);
	$y = 1 + floor($n/$k - 0.5);
	if (floor($n/$k - 0.5)<0) $y = 0;
	
	if($k%2 == 1){
		echo $x**3;
	}else{
		echo $x**3 + $y**3;
	}
	

?>