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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <iostream>

using namespace std;

int main() {
    int N, K;
    cin >> N >> K;
    int count = 0;
    for (int a = 1; a < N + 1; a++) {
        for (int b = 1; b < N + 1; b++) {
            for (int c = 1; c < N + 1; c++) {
                int aa = a + b;
                int bb = c + b;
                int cc = c + a;
                if (aa % K == 0 && bb % K == 0 && cc % K == 0) {
                    cout << "a = " << a << " b = " << b << " c = " << c << endl;
                    count++;
                }
            }
        }
    }
    cout << count << endl;
}