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: Time Limit Exceeded)

#include <iostream>

using namespace std;

int main(void)
{
  int N, K;
  cin >> N >> K;
  int num = 0;
  for(int a = 1; a <= N; a++){
    for(int k = K; k <= 2*N; k+=K){
      for(int l = K; l <= 2*N; l+=K){
        int b = k - a;
        int c = l - a;
        if(b == 0 || c == 0) continue;
        if(b > N || c > N) continue;
        if(b < 0 || c < 0) continue;
        if(((b + c) % K) == 0){
          //cout << a << " "  << b << " " << c << endl;
          num++;
        }
      }
    }


  }
  cout << num << endl;
  return 0;
}