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)

object Main extends App {
  val nk = io.StdIn.readLine().split(" ").map(_.toInt)
  val N = nk(0)
  val K = nk(1)
  val isEven = K % 2 == 0
  val zsize = (1 to N).toList.count(_ % K == 0)
  if (isEven) {
    val half = (1 to N).toList.count(_ % K == K / 2)
    val res = zsize + 3 * zsize * (zsize - 1) + zsize * (zsize - 1) * (zsize - 2) + half + 3 * half * (half - 1) + half * (half - 1) * (half - 2)
    println(res)
  }
  else {
    val res = zsize + 3 * zsize * (zsize - 1) + zsize * (zsize - 1) * (zsize - 2)
    println(res)
  }
}