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 Fortran (gfortran v4.8.4) (judge verdict: Accepted)

   Program ABC159C
   implicit none
   integer::L,i,j
   real(8)::Vmax=0,xmax,ymax,zmax,x,y,z,V

      read *,L
      do i=1,100
         x=real(L)/100.0*real(i)
         do j=1,100
            y=(real(L)-x)/100.0*real(j)
            z=real(L)-x-y
            V=x*y*z
            if (V>Vmax) then
               Vmax=V
               xmax=x
               ymax=y
               zmax=z
            end if
         end do
      end do

      do i=-50,50
         x=xmax+real(L)/10000.0*real(i)
         do j=-50,50
            y=ymax+real(L)/10000.0*real(j)
            z=real(L)-x-y
            V=x*y*z
            if (V>Vmax) then
               Vmax=V
            end if
         end do
      end do

      print *,Vmax
      stop

   End Program ABC159C