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 PHP7 (7.0.15) (judge verdict: Wrong Answer)

<?php
// C
fscanf(STDIN, '%d', $l);
$ans = 0;
$r = $l / 3;
var_dump($r ** 3);
exit;
for ($i = 0; $i < 1000; $i++) {
    for ($j = 0; $j < 1000; $j++) {
        $k = 1000 - $i - $j;
        if ($k <= 0) break;
        $ans = max($i * $j * $k, $ans);
    }
}
echo $ans . PHP_EOL;