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 <bits/stdc++.h>
#define lli long long int
#define inf 2147483647
#define infll LLONG_MAX
#define rep(i, n) for(int i=0; i<(int)(n); i++)
#define all(v) v.begin(), v.end()
#define endl "\n"
using namespace std;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(10);
    const double unit = 0.1;
    int L;
    cin >> L;
    double ans = 0;
    for(double i=unit; i<L-2*unit; i+=unit){
        for(double j=unit; j<L-i-unit; j+=unit){
            ans = max(ans, i*j*(L-i-j));
        }
    }
    cout << ans << endl;
}