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 <string>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <vector>
#include <algorithm>
#include <cstdio>
#include <queue>
#define rep(i, n) for (int i = 0; i < (n); i++)
#define int long long
#define INF 1e9 + 7
#define cae cout << ans << endl;
#define cye cout << "Yes" << endl;
#define cne cout << "No" << endl;
#define r0 return 0;
using namespace std;
typedef pair<int,int>P;
typedef long long ll;
signed main() {
    int l;
    cin >> l;
    if (l % 3 == 0) {
        cout << (l / 3)*(l / 3)*(l / 3) << endl;
    } else if (l % 3 == 1) {
        cout << (l / 3)*(l / 3)*(l / 3 + 1) << endl;
    } else if (l % 3 == 2) {
        cout << (l / 3)*(l / 3 + 1)*(l / 3 + 1) << endl;
    }
    r0
}