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 JavaScript (node.js v5.12) (judge verdict: Accepted)

"use strict"

function main(input) {
  input = input.split(/\n|\s/).map(v => ~~v)
  const N = input[0]
  const K = input[1]

  let ans = 0

  if (K % 2 === 1) {
    //奇数
    for (let i = 1; i <= N; i++) {
      if (i % K === 0) ans++
    }
    ans = Math.pow(ans, 3)
  } else {
    //偶数
    let tmp = 0
    let tmp2 = 0
    for (let i = 1; i <= N; i++) {
      if (i % K === K / 2) {
        tmp++
      }
      if (i % K === 0) {
        tmp2++
      }
    }
    ans += Math.pow(tmp, 3)
    ans += Math.pow(tmp2, 3)
  }

  console.log(ans)
}
main(require("fs").readFileSync("/dev/stdin", "utf8"))