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 Kotlin (1.3.71) (judge verdict: Accepted)

import kotlin.math.pow

fun longList() = readLine()?.split(" ")?.map(String::toLong) ?: TODO()
fun main() {
    val (n, k) = longList()

    if (n == k) {
        println("1")
        return
    }
    if (k % 2L == 1L) {
        val n2 = n / k
        println(n2.toDouble().pow(3.0).toLong().toString())
    } else {
        val n2 = (n / k).toDouble().pow(3)
        var n3 = 0
        1.until(n + 1).forEach {
            if (it % k == k / 2L) {
                n3++
            }
        }
        println((n2 + n3.toDouble().pow(3)).toLong().toString())
    }
}