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 OCaml (4.02.3) (judge verdict: Wrong Answer)

let l = read_int ()
let s = float_of_int (l/3)
let _ = (if l mod 3 = 0 then s ** 3. else
        if l mod 3 = 1 then s *. (s +. 0.5) *. (s +. 0.5) else
        (s +. 1.) *. (s +. 0.5) *. (s +. 0.5)) |> Printf.printf "%f\n"