Problem:
Score : 300 points

Problem Statement

Given is a positive integer L.
Find the maximum possible volume of a rectangular cuboid whose sum of the dimensions (not necessarily integers) is L.

Constraints

1 ≤ L ≤ 1000

L is an integer.

Input

Input is given from Standard Input in the following format:

L

Output

Print the maximum possible volume of a rectangular cuboid whose sum of the dimensions (not necessarily integers) is L.
Your output is considered correct if its absolute or relative error from our answer is at most 10^{-6}.

Sample Input 1

3

Sample Output 1

1.000000000000

For example, a rectangular cuboid whose dimensions are 0.8, 1, and 1.2 has a volume of 0.96.

On the other hand, if the dimensions are 1, 1, and 1, the volume of the rectangular cuboid is 1, which is greater.

Sample Input 2

999

Sample Output 2

36926037.000000000000

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
public class ProCon
{
    public static void Main(){     
        //string[] line1 =　Console.ReadLine().Split(' ');
        string line = Console.ReadLine();
        //long L = long.Parse(line) * 1000000;
        long L = long.Parse(line);
        long volume = 0;
        // Nが２つ選ばれたら偶数
        // Mが２つ選ばれたら偶数
        for(int i = 0; i < L; i++)
        {
            for(int j = 0; j < L; j++)
            {
                long V = (i * j * L) - (i * i * j) - (i * j * j);
                if(V>volume) volume = V;
            }
        }
        //float result = volume / 1000000;
        //Console.WriteLine(result);
        Console.WriteLine(volume);
    }
}