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 C (GCC 5.4.1) (judge verdict: Time Limit Exceeded)

#include<stdio.h>
int main() {
	int N, K, i, j, k, count = 0;
	scanf("%d %d", &N, &K);
	for (i = 1; i <= N; i++) {
		for (j = 1; j <= N; j++) {
			for (k = 1; k <= N; k++) {
				if ((i + j) % K == 0) {
					if ((j + k) % K == 0) {
						if ((k + i) % K == 0) {
							count++;
						}
					}
				}
			}
		}
	}
	printf("%d", count);
	return 0;
}