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) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		
		int N = sc.nextInt();
		
		PriorityQueue<Long> queue = new PriorityQueue<Long>(Collections.reverseOrder());
		HashSet<Long> has = new HashSet<Long>();
		
		queue.add((long) 0); queue.add((long) 0);
		for(int i = 1; i<=N; i++) {
			long n = sc.nextInt();
			if(has.contains(n)) {
				queue.add((n));
				has.remove(n);
			}
			else {
				has.add(n);
			}
		}
		
		System.out.println(queue.poll()*queue.poll());
		
	}

}
