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)

#define _GLIBCXX_DEBUG

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

constexpr ll INF = 1e16;

#define rep(i, N) for(ll i=0; i<N; ++i)

ll max(ll a, ll b) {return a < b ? b : a; }
ll min(ll a, ll b) {return a > b ? b : a; }
double maxf(double a, double b) { return a < b ? b : a; }

int main() {
  ll n;
  cin>>n;
  n = n / 3.0;

  cout<<n*n*n<<endl;

  return 0;
}