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;

public class Hello
{
    public static void Main()
    {
        // Your code here!
         int[] input = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToArray();
        int N = input[0];
        int K = input[1];
        int count = 0;

        for(int a = 1; a <= N; a++)
        {
            int b = 0;
            int n = 0;
           
            while(true) //bの値を求めるループ
            {
                n++;
                b = n * K - a;
                if(b <= 0)
                {
                    continue;
                }
                if(b > N)
                {
                    break;
                }
                
                
                int m = 0;
                int c = 0;
                while(true) //cの値を求めるループ
                {
                    m++;
                    c = m * K - a;
                    if(c <= 0)
                    {
                        continue;
                    }
                    if(c > N)
                    {
                        break;
                    }
                    if((b + c) % K == 0)
                    {
                        count++;
                        /*
                        Console.Write("a = " + a + " ");
                        Console.Write("b = " + b + " ");
                        Console.Write("c = " + c);
                        Console.WriteLine();
                        */
                    }
                    
                }
            }
            
            
        }
        Console.WriteLine(count);
    }
}