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: Time Limit Exceeded)

using System;
 
class Choku
{
    static void Main()
    {
        var l = int.Parse(Console.ReadLine());
        Console.WriteLine(Solution(l));
    }
 
    static double Solution(int l)
    {
        var step = 0.00000000001;
        var range = step * 100000;
        var start = l / 3 - range;
        var end = l / 3 + range;
        var max = .0;
 
        for (var i = start; i < end; i += step)
        {
            for (var j = start; j < end; j += step)
            {
                var v = i * j * (l - i -j);
                if (max < v)
                {
                    max = v;
                }
            }
        }
 
        return max;
    }
}