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 argc, char const *argv[]) {
	char str[101];
	int n, k;
	int a, b, c;
	int ans = 0;

	fgets(str, 100, stdin);
	sscanf(str, "%d %d\n", &n, &k);

	a = b = c = 1;

	for (a = 1; a <= n; a++) {
		for (b = 1; b <= n; b++) {
			for (c = 1; c <= n; c++) {
				if ((a+b)%k==0
						&& (b+c)%k==0
						&& (c+a)%k==0) {
						ans++;
				}
			}
		}
	}

	printf("%d\n", ans);



	return 0;
}