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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ll long long
#define REP(i, n) for (int i = 0; i < n; i++)
#define ALL(a) (a).begin(), (a).end()
typedef vector<int> vi;
const int INF = 1LL << 60; //10e18+10e17ちょっとくらい
const int MOD = 1000000007;
const int MAX_N = 200100;

signed main()
{
    //  以降 cin の入力元が 'input.txt' になる
    //std::ifstream in("input.txt");
    //std::cin.rdbuf(in.rdbuf());
    double L;
    cin >> L;
    L /= 3.;
    cout << setprecision(20) << L * L * L << endl;

    return 0;
}