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: Wrong Answer)

#include <stdio.h>

int main(){
	int n,k,count=0;
  	scanf("%d%d", &n,&k);
  
  	for(int i=k/3;i<=n-2;i++){
      for(int j=1;j<=i;j++){
        for(int l=1;l<=j;l++){
			if((i+j)%k==0 && (j+l)%k==0 && (l+i)%k==0){
				if(i==j && j==l){
					count++;
                }else if(i!=j && j!=l && l!=i){
					count+=6;
                }else{
					count+=3;
                }
            }
        }
      }
    }
  	printf("%d", count);
}