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

int A[100100];

int main(){
	int n;
	vector<long long> v;
	
	cin >> n;
	for(int i=0;i<n;i++){
		cin >> A[i];
	}
	sort(A,A+n);
	reverse(A,A+n);
	
	for(int i=1;i<n;i++){
		if(A[i-1]==A[i]){
			v.push_back(A[i]);
			i++;
		}
		if(v.size()==2){
			cout << v[0]*v[1] << endl;
			return 0;
		}
	}
	
	cout << 0 << 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<bits/stdc++.h>
using namespace std;

int A[100100];

int main(){
	int n;
	vector<long long> v;
	
	cin >> n;
	for(int i=0;i<n;i++){
		cin >> A[i];
	}
	sort(A,A+n);
	reverse(A,A+n);
	
	for(int i=1;i<n;i++){
		if(A[i-1]==A[i]){
			v.push_back(A[i]);
			i++;
		}
		if(v.size()==2){
			cout << v[0]*v[1] << endl;
			return 0;
		}
	}
	
	cout << 0 << endl;
	return 0;
}
```