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.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Scanner;

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();
		Map<Integer, Integer> map = new HashMap<>();
		for(int i = 0 ; i < n ; i++) {
			if(map.containsKey(a[i])) {
				map.put(a[i], map.get(a[i]) + 1);
			} else {
				map.put(a[i], 1);
			}
		}
		List<Entry<Integer, Integer>> entry = new ArrayList<>(map.entrySet());
		Collections.sort(entry, new Comparator<Entry<Integer, Integer>>() {
			public int compare(Entry<Integer, Integer> obj1, Entry<Integer, Integer> obj2) {
				if(obj1.getValue() >= 2 && obj2.getValue() >= 2) return obj2.getKey() - obj1.getKey();
				else return obj2.getValue() - obj1.getValue();
			}
		});
		if(entry.get(0).getValue() >= 4) {
			System.out.println(1L * entry.get(0).getKey() * entry.get(0).getKey());
		} else if(entry.get(0).getValue() >= 2 && entry.get(1).getValue() >= 2) {
			System.out.println(1L * entry.get(0).getKey() * entry.get(1).getKey());
		} else {
			System.out.println(0);
		}
	}
}