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
#include"cstdio"
#include"algorithm"
using namespace std;
bool cmp(int a,int b)
{
 return a>b;
}
int main(){
	int n;
	scanf("%d",&n);
	int b[100005];
	int i=0,j=0,max=0,min=0;
	for(i=0;i<n;i++)
	{
		scanf("%d",&b[i]);
	}	
	long long sum=1;
	int t=0;
	sort(b,b+n,cmp);
	for(i=1;i<n;i++)
	{
		if(b[i]==b[i-1])
		{
			sum=sum*b[i];
			i++;
			t++;
		}
		if(t==2)
			break;		
	}
	if(sum==1&&t!=2)
		sum=0;
	printf("%lld\n",sum);
	return 0;
}
