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<iostream>
#include<algorithm>
#include<cstdio>
using namespace std; 
long long a[100020]={0}; 
int main ()
{
	int i,n;
	while(cin>>n)
	{
		for(i=0;i<n;i++)
		scanf("%lld",&a[i]);
		sort(a,a+n);
		long long t=1,m=0;
		for(i=n-1;i>0;i--)
		{
			if(a[i]==a[i-1])
			{
				t=a[i]*t;
				a[i-1]=0;
				m++;
			}
		if(m>=2)
			break;
		}
		if(m<2)
		cout<<"0"<<endl;
		else
		cout<<t<<endl;
	}
	
	return 0;
} 