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 _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for (ll i = (ll)(a); i < (ll)(b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
#define ALL(x) x.begin(), x.end()
using namespace std;
using ll = long long;
using lld = long double;
using VI = vector<int>;
using VVI = vector<VI>;
using PII = pair<int, int>;
const int IINF = 1 << 30;
const ll INF = 1ll << 60;
const ll MOD = (1'000'000'000 + 7);

bool is_ok(string s)
{
    int n = s.size();
    rep(i, n / 2)
    {
        if (s[i] != s[n - 1 - i])
        {
            return false;
        }
    }
    return true;
}

int main()
{
    lld l;
    cin >> l;
    cout << fixed << setprecision(18) << (l / 3.0) * (l / 3.0) * (l / 3.0) << endl;
    return 0;
}