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: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using static System.Console;
using static System.Math;

namespace Atcoder
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                Solve.Answer();
            }
            catch (Exception ex)
            {
                WriteLine(ex.ToString());
            }
        }
    }

    public class Solve
    {
        public static void Answer()
        {
            var L = IO_ShortCut.ReadDouble;
            var L3 = (double)L / 3;

            WriteLine(L3 * L3 * L3);
        }
    }

    public class IO_ShortCut
    {
        #region Input
        public static string ReadString => ReadLine();
        public static int ReadInt => int.Parse(ReadLine());
        public static long ReadLong => long.Parse(ReadLine());
        public static double ReadDouble => double.Parse(ReadLine());

        public static List<string> ReadSplitString => ReadLine().Split().ToList();
        public static List<int> ReadSplitInt => ReadLine().Split().Select(s => int.Parse(s)).ToList();
        public static List<long> ReadSplitLong => ReadLine().Split().Select(s => long.Parse(s)).ToList();
        public static List<double> ReadSplitdouble => ReadLine().Split().Select(s => double.Parse(s)).ToList();
        #endregion

        #region Output
        public static void OutJoinSpace<T>(IEnumerable<T> list) => WriteLine(string.Join(" ", list));
        public static void WriteLineYes_or_No(bool flag) => WriteLine(flag ? "Yes" : "No");

        #endregion
    }

    /// <summary>
    /// 正の数の四則演算のみ対応
    /// </summary>
    public class Mod
    {
        // 割る数の定義
        private readonly static long M = 1000000007;

        // 足し算
        public static long Add(long a, long b) => (a * b) % M;
        // 引き算
        public static long Sub(long a, long b) => (a - b) % M >= 0 ? (a - b) % M : (a - b) % M + M;
        // 掛け算
        public static long Multi(long a, long b) => (a * b) % M;
    }

    public class MathLib
    {
        public static int Cmb(int n, int k)
        {
            var a = 1;
            for (int i = 0; i < k; i++)
            {
                a *= n;
                n--;
            }
            return k == 0 ? 1 : a / k;
        }
    }
}