#include<bits/stdc++.h>
using namespace std;

int main(){
  long long n;
  cin>>n;
  long long a[n];
  for(int i=0;i<n;i++){
      cin>>a[i];
  }
  sort(a,a+n);
  long long b=0,c=0;
  int i=n-2;
  while(i>=0&&(b==0||c==0)){
      
      if(a[i]==a[i+1]){
        
        
        if(b==0) b=a[i];
        else c=a[i];
        
        i-=2;
      }
      else i--;
  }
  cout<<b*c<<endl;
  
}
### Prompt

Please create a solution in CPP to the following problem:

We have N sticks with negligible thickness. The length of the i-th stick is A_i.

Snuke wants to select four different sticks from these sticks and form a rectangle (including a square), using the sticks as its sides. Find the maximum possible area of the rectangle.

Constraints

* 4 \leq N \leq 10^5
* 1 \leq A_i \leq 10^9
* A_i is an integer.

Input

Input is given from Standard Input in the following format:


N
A_1 A_2 ... A_N


Output

Print the maximum possible area of the rectangle. If no rectangle can be formed, print 0.

Examples

Input

6
3 1 2 4 2 1


Output

2


Input

4
1 2 3 4


Output

0


Input

10
3 3 3 3 4 4 4 5 5 5


Output

20

### Response

```cpp
#include<bits/stdc++.h>
using namespace std;

int main(){
  long long n;
  cin>>n;
  long long a[n];
  for(int i=0;i<n;i++){
      cin>>a[i];
  }
  sort(a,a+n);
  long long b=0,c=0;
  int i=n-2;
  while(i>=0&&(b==0||c==0)){
      
      if(a[i]==a[i+1]){
        
        
        if(b==0) b=a[i];
        else c=a[i];
        
        i-=2;
      }
      else i--;
  }
  cout<<b*c<<endl;
  
}
```