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 mp make_pair
#define mod 1000000007
#define INF 1e9+5
typedef long long ll;
#define IOS ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define forn(i,a,b) for(ll i=a;i<(ll)b;i++)
#define ff first
#define ss second
int check(string s)
{
	int n=s.length();
	for(int i=0;i<n/2;i++)
	{
		if(s[i]!=s[n-i-1])
			return 0;
	}
	return 1;
}
int32_t main()
{
	IOS;
	double n;
	cin>>n;
	cout<<(setprecision)(9)<<(n*n*n)/27<<"\n";
	return 0;
}