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: Wrong Answer)

#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
int main()
{
    ll n,b,p,q,r,a;
    double s,s1,s2;
    cin>>n;
    if(n%3==0)
    {
        p=(n/3);
        s=p*p*p;
    }
    else
    {
        a=n%3;
        p=n/3;q=n/3;r=n/3;
        if(a==1)
        {
            p++;
            s=p*q*r;
        }
        else
        {
            p++;q++;
            s1=p*q*r;
            p=p+2;
            s2=p*q*r;
            if(s1>s2){s=s1;}
            else{s=s2;}
        }
    }
    printf("%0.6lf \n",s);
   // cout<<s<<"\n";
}