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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.io.InputStream;
import java.io.PrintStream;
import java.util.Scanner;

public class Main {
	InputStream in = System.in;
	PrintStream out = System.out;

	public void _main(String[] args) {
		Scanner sc = new Scanner(in);

		int N = sc.nextInt();
		int K = sc.nextInt();

		int ans = 0;
		for (int a = 1; a <= N; a++) {
			for (int b = 1; b <= N; b++) {
				if ((a + b) % K != 0) {
					continue;
				}
				if (a % K != b % K) {
					continue;
				}

				int ck = (K - (a % K)) ;
				//1～Nで mod Kがckのものの数
				int x = N / K; //1～Nに、Kが何周期あるか。
				//周期に含まれない部分（最後の部分）に、mod Kがckのものが含まれるなら+1する
				if (N % K >= ck) {
					x++;
				}
				ans += (x);

			}
		}

		out.println(ans);

		sc.close();

	}

	public static void main(String[] args) {
		new Main()._main(args);
	}

}