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