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();
        TreeMap<Integer, Integer> map = new TreeMap<>(Collections.reverseOrder());
        for(int i = 0; i < n; i++) {
            int num = sc.nextInt();
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        int count = 2;
        long area = 1;
        Iterator entries = map.entrySet().iterator();
        while(entries.hasNext()) {
            Map.Entry entry = (Map.Entry)entries.next();
            int value = (Integer)entry.getValue();
            while(value >= 2 && count != 0) {
                area *= (Integer) entry.getKey();
                value -= 2;
                count--;
            }
            if(count == 0) break;
        }
        if(count == 0) {
            System.out.println(area);
        } else {
            System.out.println(0);
        }
    }
}
