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.*;
import java.util.stream.*;

public class Main {

	public static void main(String[] args) {
		Main main = new Main();
		main.run();
	}


	public void run() {
		Scanner sc = new Scanner(System.in);
		int n=sc.nextInt();
		Map<Long,Long>cnt = new HashMap<>();
		List<Long> a = new ArrayList<>();
		for(int i=0; i<n; i++) {
			long v=sc.nextLong();
			cnt.put(v, cnt.containsKey(v) ? cnt.get(v)+1 : 1);
			a.add(v);
		}
		Collections.sort(a);
		a = a.stream().distinct().collect(Collectors.toList());
		ArrayList<Long> ans = new ArrayList<>();
		for(int i=a.size()-1; i>=0; i--) {
			long v=a.get(i);
			if(cnt.get(v) >= 4) {
				ans.add(v);
				ans.add(v);
			}else if(cnt.get(v)>=2) {
				ans.add(v);
			}
			if(ans.size()>=2) break;
		}
		if(ans.size()<1){
			System.out.println(0);
		}else {
			System.out.println(ans.get(0)*ans.get(1));
		}
		sc.close();
	}





}
