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

int main(){
	int n;cin>>n;
	int a[n];
	for(int i=0;i<n;++i){
		cin>>a[i];
	}
	sort(a,a+n);
	int f=0,s=0;
	for(int i=0;i<n;i+=2){
		if(a[i]==a[i+1]){
			s=f;
			f=a[i];
		}else{
			i--;
		}
	}
	cout<<(long long)s*f<<endl;
}

### Prompt

Your task is to create 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;cin>>n;
	int a[n];
	for(int i=0;i<n;++i){
		cin>>a[i];
	}
	sort(a,a+n);
	int f=0,s=0;
	for(int i=0;i<n;i+=2){
		if(a[i]==a[i+1]){
			s=f;
			f=a[i];
		}else{
			i--;
		}
	}
	cout<<(long long)s*f<<endl;
}

```