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;
signed main(){
  int l;
  int x,y,z;
  double sum=0;
  cin>>l;
  for(double i=0;i<l;i++){
    for(double j=0;j<l;j++){
      if(l-i+j>0){
        if(sum<j*i*(l-(j+i))){
          sum=j*i*(l-(j+i));
          x=i,y=j,z=(l-(j+i));
        }
      }
    }
  }
  for(int i=x-1;i<x+1;i++){
    for(int j=y-1;j<y+1;j++){
      for(int k=z-1;k<z+1;k++){
        if(i+j+k==l){
          if(sum<i*j*k){
            sum=i*j*k;
          }
        }
      }
    }
  }
  cout<<fixed<<sum<<"\n";
}