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)

#include<iostream>
#include<vector>
#include<algorithm>
#include<iomanip>
#include<utility>
#include<iomanip>
#include<map>
#include<cmath>
#include<cstdio>
#define rep(i,n) for(int i=0; i<(n); ++i)
using namespace std;
using ll =long long;
using P = pair<int,int>;

int main(){
    int l;
    cin >> l;
    int t = l/3;
    int a = l%3;
    if(a>=2){
        cout << t*(t+a/2)*(t+a/2) << endl;
        return 0;
    }
    cout << t*t*(t+a) << endl;
    return 0;
}