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

int main() {
  int n,x;
  cin>>n;
  x=0;
  vector<long int> a(n);
  vector<long int> b(n,0);
  for(int i=0;i<n;i++){
    cin>>a.at(i);
  }
  sort(a.begin(),a.end());
  reverse(a.begin(),a.end());
  
  for(int i=0;i<n-1;i++){
    if(a.at(i)==a.at(i+1)){
      b.at(x)=a.at(i);
      x++;
      i++;
    }
    if(x>1)break;
  }
  cout<<b.at(0)*b.at(1)<<endl;
}
### Prompt

Please formulate a CPP solution 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() {
  int n,x;
  cin>>n;
  x=0;
  vector<long int> a(n);
  vector<long int> b(n,0);
  for(int i=0;i<n;i++){
    cin>>a.at(i);
  }
  sort(a.begin(),a.end());
  reverse(a.begin(),a.end());
  
  for(int i=0;i<n-1;i++){
    if(a.at(i)==a.at(i+1)){
      b.at(x)=a.at(i);
      x++;
      i++;
    }
    if(x>1)break;
  }
  cout<<b.at(0)*b.at(1)<<endl;
}
```