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.io.*;
import java.util.*;
public class Main
{
	public static void main(String[] args) throws IOException
	{
		Scanner c = new Scanner(System.in);
		int N = c.nextInt();
		TreeMap<Integer, Integer> map = new TreeMap<Integer, Integer>();
		for(int j=0; j<N; j++)
		{
			int i = c.nextInt();
			if(!map.containsKey(-i)) map.put(-i, 1);
			else map.put(-i, 1+map.get(-i));
		}
//		System.out.println(map);
		int side1=0, side2=0;
		for(int i: map.keySet())
		{
			if(map.get(i) >= 2)
			{
				if(side1 == 0 && map.get(i)>=4)
				{
					System.out.println(((long)(i)) * (long)(i));
					return;
				}
				else if(side1 == 0)
				{
					side1 = i;
				}
				else
				{
					System.out.println(((long) (side1)) * (long) (i));
					return;
				}
			}
		}
		System.out.println(0);
	}
}
