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
import java.util.*;
public class Main{
	public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
      int n = sc.nextInt();
      int[] a = new int[n];
      for(int i = 0;i < n;i++)a[i]=sc.nextInt();
      Arrays.sort(a);
      long x = 1;
      List<Integer> list = new ArrayList<Integer>();
      for(int i = n-1;i > 0;i--){
      	if(a[i]==a[i-1]&&list.size()<=1){
          x *= (long)a[i];
          list.add(a[i]);
          i--;
        }
        if(list.size()==2)break;
      }
      if(list.size()<=1)System.out.println(0);
      else System.out.println(x);
    }
}
