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 Scala (2.11.7) (judge verdict: Wrong Answer)

// C - Triangular Relationship
// https://abc108.contest.atcoder.jp/tasks/arc102_a

import scala.io.StdIn.readLine

object Main extends App {

  val Array(n, k) = readLine.split(" ").map(_.toInt)

  val twoPair: Seq[(Int, Int)] = (k to n*2 by k).flatMap(x => (1 to x/2).filter(y => x-y <= n).map(y => (y, x-y)))

  val (sameTwoPair, diffTwoPair) = twoPair.partition(p => p._1 == p._2)
  val sameKeys = sameTwoPair.map(_._1).toSet

  val diffThreeTrio = diffTwoPair.filter(p => sameKeys.contains(p._1) && sameKeys.contains(p._2))

  val count = sameTwoPair.length + (diffThreeTrio.length * 6)

  println(count)

}