#include<bits/stdc++.h>
using namespace std;
int main() {
	vector<int>v;
	int n;
	cin>>n;
	int a[n+3];
	for(int i=0;i<n;i++)
	cin>>a[i];
	sort(a,a+n,greater<int>());
	for(int i=0;i<n;i++)
	{
		if(a[i]==a[i+1])
	    {
	    	v.push_back(a[i]);
	    	i++;
	    }
	    if(v.size()==2)
	    {
	    	cout<<1LL*v[0]*v[1];
	    	return 0;
	    }
	}
	cout<<"0";
	return 0;
}
### Prompt

Generate 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() {
	vector<int>v;
	int n;
	cin>>n;
	int a[n+3];
	for(int i=0;i<n;i++)
	cin>>a[i];
	sort(a,a+n,greater<int>());
	for(int i=0;i<n;i++)
	{
		if(a[i]==a[i+1])
	    {
	    	v.push_back(a[i]);
	    	i++;
	    }
	    if(v.size()==2)
	    {
	    	cout<<1LL*v[0]*v[1];
	    	return 0;
	    }
	}
	cout<<"0";
	return 0;
}
```