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: Wrong Answer)

function Main(input) {
  input = input.split("\n");
  var n = parseInt(input[0].split(" ")[0]);
  var k = parseInt(input[0].split(" ")[1]);
  var ans =0;
  if(k<=n){
    if(k%2==0){
      ans=Math.pow(Math.floor(n/k),3)+Math.pow(Math.floor(n/(k/2))-Math.floor(n/k),3);
      //ans=Math.pow(Math.floor(n/(k/2)),3);
    }else{
      ans=Math.pow(Math.floor(n/k),3);
    }
  }
  console.log('%s', ans);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));