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>
#define rep(i, start, end) for (long long int i = start; i < end; ++i)
#define srt(x) sort((x).begin(), (x).end());
#define rsrt(x) sort((x).rbegin(), (x).rend());
#define deb(x) cout<<#x<<" = "<<(x)<<" (L"<<LINE<<")"<<endl;
#define vdeb(x) {cout<<#x<<" = { "; rep(i, x.size()) cout<<x[i]<<' '; cout <<'}'<<" (L"<<LINE<<")"<<endl;}
using namespace std;
using ll = long long int;
using vi = vector<int>;
using vivi = vector<vi>;
using vll = vector<long long int>;
using vs = vector<string>;

int main()
{
    int L;
    cin >> L;
    cout << setprecision(20) << pow(L / 3.0, 3.0) << endl;
}