#include<bits/stdc++.h>
using namespace std;
int main(){
  int n,i,j,k;
  cin>>n;
  double a[n],ans=0,x,y;
  for(i=0;i<n;i++) cin>>a[i];
  sort(a,a+n);
  for(i=0;i<n;i++){
    for(j=i+1;j<n;j++){
      k=n-1;
      while(k==i||k==j) k--;
      x=a[k];k--;
      while(k==i||k==j) k--;
      y=a[k];
      ans=max(ans,(x+y)/(a[j]-a[i]));
    }
  }
  printf("%6lf\n",ans);
  return 0;
}
### Prompt

In cpp, your task is to solve the following problem:

N different natural numbers are given. If you select four different ones and set them as $ A $, $ B $, $ C $, $ D $, the following formula

$ \ Frac {A + B} {C --D} $



I want to find the maximum value of.




Given N different natural numbers, choose 4 different from them and create a program to find the maximum value of the above formula.



Input

The input is given in the following format.


N
a1 a2 ... aN


The number N (4 ≤ N ≤ 1000) of natural numbers is given in the first line. The value ai (1 ≤ ai ≤ 108) of each natural number is given in the second line. However, the same natural number does not appear more than once (ai ≠ aj for i ≠ j).

Output

Outputs the maximum value of the above formula as a real number for a given N natural numbers. However, the error must not exceed plus or minus 10-5.

Examples

Input

10
1 2 3 4 5 6 7 8 9 10


Output

19.00000


Input

5
22 100 42 3 86


Output

9.78947


Input

6
15 21 36 10 34 5


Output

18.00000


Input

4
100000 99999 8 1


Output

28571.285714

### Response

```cpp
#include<bits/stdc++.h>
using namespace std;
int main(){
  int n,i,j,k;
  cin>>n;
  double a[n],ans=0,x,y;
  for(i=0;i<n;i++) cin>>a[i];
  sort(a,a+n);
  for(i=0;i<n;i++){
    for(j=i+1;j<n;j++){
      k=n-1;
      while(k==i||k==j) k--;
      x=a[k];k--;
      while(k==i||k==j) k--;
      y=a[k];
      ans=max(ans,(x+y)/(a[j]-a[i]));
    }
  }
  printf("%6lf\n",ans);
  return 0;
}
```