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;
    int x, y, z;
    int sumA, sumB, sumC;
    int cn;
    cn = 0;
    scanf("%d %d", &n, &k);

    for (x = 1; x < n + 1; x++)
    {
        for (y = 1; y < n + 1; y++)
        {
            sumA = (x + y) % k;
            if (sumA == 0)
            {
                for (z = 1; z < n + 1; z++)
                { //(i,j,l)
                    sumB = (y + z) % k;
                    sumC = (z + x) % k;
                    if (sumB == 0 && sumC == 0)
                    {
                        cn++;
                    }
                }
            }
        }
    }
    printf("%d\n", cn);
    return 0;
}