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 rep(i, n) for (int i = 0; i < (n); i++)
#define rep1(i, n) for (int i = 1; i < (n); i++)
#define erep(i, n) for (int i = 0; i <= (n); i++)
#define erep1(i, n) for (int i = 1; i <= (n); i++)
using namespace std;
using ll = long long;

int main() {
    int L;
    cin >> L;
    double max=0;
    int k;
    double tmp;
    for (int i = 1; i <= 1000; i++) {
        for (int j = 1;i+j<=1000;j++){
            k = L - i - j;
            tmp = i * j * k;
            if (L == i + j + k) {
                if(max<tmp){
                    max = tmp;
                }
            }
        }
    }
    printf("%.13lf\n", max);
}