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 pb push_back
#define rep(i,n) for(ll i=0;i<n;i++)
#define rep1(i,n) for(ll i=1;i<=n;i++)
#define mp make_pair
#define F first
#define S second
#define pf pop_front
#define IOS ios_base::sync_with_stdio(0); cin.tie(0)
typedef long long ll;
const ll mod=1e9+7;
const ll maxn=3005;
const ll inf=1e9+7;
double dp[maxn][maxn];
double p[maxn];
double n;
int main()
{
    while(cin>>n)
    {
        double a=n/3,b=n/3;
        double c=n-a-b;
        cout<<fixed<<setprecision(6)<<a*b*c<<"\n";
    }
}