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<bits/stdc++.h>
using namespace std;
long long a[1000000],n,p[100000],len,l1,l2,t;
int main(){
    cin>>n;
    for(int i=1;i<=n;i++){
    	cin>>a[i];
	}
	sort(a+1,a+1+n);
//	for(int i=1;i<=len;i++)cout<<a[i]<<" ";
	for(int i=n;i>=1;i--){
	    if(a[i]==a[i-1]){
		    p[++t]=a[i];
			i--;
			if(t==2)break; 
		} 
	}
	cout<<p[1]*p[2];
    return 0;
}