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# (Mono 4.6.2.0) (judge verdict: Time Limit Exceeded)

using System;


class Program
{
    static void Main(string[] args)
    {
        string[] input = Console.ReadLine().Split(' ');
        int n = int.Parse(input[0]);
        int k = int.Parse(input[1]);
        int a, b, c;
        int count=0;
        for(a = 1; a < n+1; a++)
        {                
            for (b = 1; b < n +1; b++)
            {
                if ((a + b) % k == 0)
                {
                    for (c = 1; c < n + 1; c++)
                    {                       
                            if ((b + c) % k == 0)
                            {
                                if ((c + a) % k == 0)
                                {
                                    count++;
                                }
                            }                      
                    }
                }
            }

        }

        Console.WriteLine(count);
        
    }
}