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: Time Limit Exceeded)


import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int k = sc.nextInt();
int count = 0;
int count2=0,count3=0;

for(int a=1;a<=n;a++) {
	for(int b=a;b<=n;b++) {
		if((a+b)%k != 0) {
			continue;
		}
		for(int c=b;c<=n;c++) {
		if((a+c)%k != 0) {
			continue;
		}
		if((b+c)%k != 0) {
			continue;
		}
		count++;
		if(a==c) {count3++;}else
		if(a==b || b==c) {count2++;}
		}
	}
}

System.out.println((count*6)-(count2*3)-(count3*5));

sc.close();
	}

}