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 $10^{-6}$.