#include <iostream>
#include <algorithm>
using namespace std;
int main(){
	long long n,i;
	cin>>n;
	long long a[n];
	for (i=0;i<n;i++)cin>>a[i];
	sort(a,a+n);
	i=0;
	long long ans=0;
	while(i<n-1){
		//cout<<i<<n<<endl;
		///Sleep(500);
		if (a[i]==a[i+1]){
			int j=i+2;
			i++;
			if (j>=n)continue;
			while(j<n-1&&a[j]!=a[j+1])j++;
			if (j<n-1)ans=max(ans,a[j]*a[i]);
		}
		else i++;
	}
	cout<<ans<<endl;
	return 0;
}

### Prompt

In Cpp, your task is to solve 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 <iostream>
#include <algorithm>
using namespace std;
int main(){
	long long n,i;
	cin>>n;
	long long a[n];
	for (i=0;i<n;i++)cin>>a[i];
	sort(a,a+n);
	i=0;
	long long ans=0;
	while(i<n-1){
		//cout<<i<<n<<endl;
		///Sleep(500);
		if (a[i]==a[i+1]){
			int j=i+2;
			i++;
			if (j>=n)continue;
			while(j<n-1&&a[j]!=a[j+1])j++;
			if (j<n-1)ans=max(ans,a[j]*a[i]);
		}
		else i++;
	}
	cout<<ans<<endl;
	return 0;
}

```