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>
using namespace std;
 
using ll = long long;
using db = double;
using pii = pair < int, int >;
using pll = pair < ll, ll >;
const int N = 2e5 + 10;
const ll inf = 1e15 + 42;
#define endl "\n"
const ll mod = 1000000007;
 
void testCase() {
    db l;
    cin >> l;
    db ans = 0;
    db inc = 1;
    if (l == 1) {
        db ans = (0.3*0.3*0.4);
        cout << fixed << setprecision(16) << ans << endl;
        return;
    }
    if (l == 2) {
        db ans = (0.6*0.7*0.7);
        cout << fixed << setprecision(16) << ans << endl;
        return;
    }
    for (db i=1; i<l; i+=inc) {
        for (db j=1; j<l; j+=inc) {
            db k = l-i-j;
            if (k < 0)
                continue;
            db v = (i*j*k);
            if (v >= ans) {
                //cout << i << " " << j << " " << k << endl;
                ans = v;           
            }
        }
    }
    cout << fixed << setprecision(15) << ans << endl;
}
 
int main() {
    ios_base :: sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    testCase();
    return 0;
}