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 C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <limits.h>
#include <string.h>

int main(void) {
 int L;
 scanf("%d",&L);
 double test = L/3;
 double res = L/3 * L/3 * L/3;
 double a1=L/3;
 double a2=L/3;
 double a3=L/3;
 double max= res;
 double res1=0;
 double  eps = 10e-14;
 for (double k=0.0;k<L;k++)
 {
     res1 = (a1+k)*(a2-k)*a3;
   if (max<res1)max=res1;
 }
 printf("%lf",max+eps);

 return EXIT_SUCCESS;
}