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<map>
using namespace std;
map<int,int> M;
int max(int a,int b) {return a>b?a:b;}
int main()
{
	int n,x,a=0,b=0;
	scanf("%d",&n);
	for(int i=1;i<=n;i++) 
	{
		scanf("%d",&x);
		if(M[x])
		{
			if(x>a&&x>b) {a=b;b=x;}
			else if(x>a) a=x;
			M[x]=0;
		}
		else M[x]=1;
	}
	printf("%lld\n",(long long)a*b);
	return 0;
}