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.Collections.Generic;
using System.Linq;

namespace ConsoleApp23
{
    class Program
    {
        static void Main(string[] args)
        {
            var line = Console.ReadLine().Trim().Split(' ').Select(s => int.Parse(s)).ToList();
            var N = line[0];
            var K = line[1];
            var answer = 0;

            for (int i = 1; i <= N; i++)
            {
                for (int j = 1; j <= N; j++)
                {
                    if((i + j) % K != 0) continue;

                    for (int k = 1; k <= N; k++)
                    {
                        if((j + k) % K == 0 && (k + i) % K == 0)
                        {
                            answer++;
                        }
                    }
                }
            }

            Console.WriteLine(answer);
        }

    }

}