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 Ruby (2.3.3) (judge verdict: Accepted)

l = gets.chomp.to_i

a = l / 3
b, c = a, a
if l % 3 == 1
  a += 0.333333333333
  b += 0.333333333333
  c += 0.333333333334
elsif l % 3 == 2
  a += 0.666666666666
  b += 0.666666666667
  c += 0.666666666667
end
print "#{sprintf("%.12f", a * b * c)}\n"