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){
    // Your code here!
    int N,K,q,p,r,MAXq,maxp;
    long count = 0;
    scanf("%d %d",&N,&K);
    MAXq = 2*N/K;
    
    for(p = N; p >= 1; p--)
    {
        for(q = (N+p)/K; q*K-p >= 1; q--)
        {
            for(int protoq = (N+p)/K; protoq*K-p >= 1; protoq--)
            {
                r = protoq*K-p;
                if((r-p)%K == 0)
                {
                    count++;
                    //printf("(%d,%d,%d)\n",p,q*K-p,r);
                }
            }
        }
    }
    printf("%ld\n",count);   
}