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: Wrong Answer)

#pragma GCC optimize("-Ofast","-funroll-all-loops","-ffast-math")
#include<bits/stdc++.h>
using namespace std;
using ll=long long;
using pii=pair<int,int>;
using pll=pair<ll,ll>;
using vi=vector<int>;
using vll=vector<ll>;
#define endl "\n"
const int mod=1e9+7;
const double pi=acos(-1.0);

int main(int argc, char const *argv[])
{
    /*#ifndef ONLINE_JUDGE
      freopen("input.txt","r",stdin);
      freopen("output.txt","w",stdout);
    #endif */
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(0);
    double l;
    cin>>l;
    double ans=(l/3)*(l/3)*(l/3);
    cout<<ans<<endl;
}