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;
using System.Linq;

namespace atcoder
{
    public class atcoder
    {
        public static void Main()
        {
            int[] input = Console.ReadLine().Split().Select(x => int.Parse(x)).ToArray();
            int n = input[0], k = input[1];
            int count = 0;
            for (int i = 1; i <= n; i++) {
                for (int j = 1; j <= n; j++)
                {
                    for (int l = 1; l <= n; l++)
                    {
                        if ((i + j) % k == 0 && (j + l) % k == 0 && (i + l) % k == 0) count++;
                    }
                }
            }
            Console.WriteLine(count);
        }
    }
}