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(void){
	int n,k,i,j,c;
	int kosu = 0;
	
	scanf("%d %d",&n,&k);
	for(i = 1;i < n + 1;i++){
		for(j = 1;k * j - i < n + 1;j++){
			if(j * k - i > 0){
				for(c = 1;k * c - i < n + 1;c++){
					if(k * c - i > 0 && (k * (j + c) - i * 2) % k == 0){
					kosu++;
					}
				}
			}
		}
	}
	printf("%d\n",kosu);
	return 0;
}