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++14 (GCC 5.4.1) (judge verdict: Accepted)

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

#define tnum long long

#define loop(i,end) for(int i = 0; i < end; i++)

tnum *inputNumbers(tnum num) {
	tnum *ret;
	ret = (tnum *)malloc(num * sizeof(num));
	loop(i, num) {
		scanf("%lld", &ret[i]);
	}
	return ret;
}


/*main code*/


int main(int argc, char *argv[]) {
	tnum l;
	tnum res;
	double r;

	scanf("%lld", &l);
	
	r = l * l * l / 27.0;

	printf("%.10f", r);

	return 0;
}