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 Rust (1.15.1) (judge verdict: Accepted)

use std::io::*;

fn read(s: &mut StdinLock) -> f64 {
    s.by_ref().bytes().map(|c| c.unwrap() as char)
        .take_while(|c| !c.is_whitespace())
        .skip_while(|c| c.is_whitespace())
        .fold(0.0, |a, x| (x as u8 - b'0') as f64 + a * 10.0)
}

fn main() {
    let s = stdin();
    let mut s = s.lock();
    let l = read(&mut s);
    println!("{:.12}", l*l*l/3.0/3.0/3.0);
}