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.util.*;
class Main
{
    public static void main (String[] args)
    {
        Scanner sc = new Scanner(System.in);

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

        int ans = 0;

        if(K > N * 3){
            ans = 0;
        }
        else if(K > N * 2){
            ans = (K - 2) * (K - 1) / 2;
        }
        else if(K > N){
            ans = (K - 2) * (K - 1) / 2 + (2 * K - 2) * (2 * K - 1) / 2;; 
        }
        else if(K == 1){
            ans = (int) Math.pow(N, 3);
        }
        else if(K == 2){
            ans += (int) Math.pow((N/2), 3) + (int) Math.pow( ( ( N + 1 ) / 2 ), 3);
        }
        else if(K % 2 == 0){
            K /= 2;
            int KK = N/K;
            ans += (int) Math.pow((KK/2), 3) + (int) Math.pow( ( ( KK + 1 ) / 2 ), 3);
        }
        else if(K % 2 == 1){
            ans += (int) Math.pow( (N/K) , 3);
        }
        System.out.println(ans);
    }
}