#include <bits/stdc++.h>
using namespace std;
int n,a[100000],num;
long long ans=1;
int main(){
  cin>>n;
  for(int i=0;i<n;i++){
    cin>>a[i];
  }
  sort(a,a+n);
  for(int i=n-1;i;i--){
    if(a[i]==a[i-1]){
      ans*=a[i];
      i--;
      num++;
    }
    if(num==2){
      cout<<ans;
      return 0;
    }
  }
  cout<<0;
  return 0;
}
### Prompt

Create a solution in CPP for 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 n,a[100000],num;
long long ans=1;
int main(){
  cin>>n;
  for(int i=0;i<n;i++){
    cin>>a[i];
  }
  sort(a,a+n);
  for(int i=n-1;i;i--){
    if(a[i]==a[i-1]){
      ans*=a[i];
      i--;
      num++;
    }
    if(num==2){
      cout<<ans;
      return 0;
    }
  }
  cout<<0;
  return 0;
}
```