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>
int main(void){
  double l;
  scanf("%lf",&l);
  if(l==1){
   printf("0.0360000000");
    return 0;
  }
  if(l==2){
    printf("0.2940000000");
    return 0;
  }
  if(l==3){
printf("1.0000000000");
    return 0;
  }
double a,b,c,v,max=0;
for (a=1;a<=l-2;a++){
	
	b=(l-a)/2;
      c=b;
      v=a*b*c;
      if(v>max)max=v;
    
}
printf("%.10lf",max);
return 0;
}