#include<stdio.h>
#include<algorithm>
using namespace std;
int main(void)
{
	int n,i;
	long long a[100000],x;
	scanf("%d",&n);
	for(i=0;i<n;i++) scanf("%lld",&a[i]);
	sort(a,a+n);
	printf("\n");
	
	x=0;
	for(i=n-1;i>0;i--){
		if(a[i]==a[i-1]){
			if(x!=0) break;
			x=a[i];
			i--;
		}
	}
	x=x*a[i];
	printf("%lld",x);
	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<stdio.h>
#include<algorithm>
using namespace std;
int main(void)
{
	int n,i;
	long long a[100000],x;
	scanf("%d",&n);
	for(i=0;i<n;i++) scanf("%lld",&a[i]);
	sort(a,a+n);
	printf("\n");
	
	x=0;
	for(i=n-1;i>0;i--){
		if(a[i]==a[i-1]){
			if(x!=0) break;
			x=a[i];
			i--;
		}
	}
	x=x*a[i];
	printf("%lld",x);
	return 0;
}
```