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 {

    Scanner sc = new Scanner(System.in);

    int MOD = (int)998244353;

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

    void run() {

        int n = sc.nextInt();

        Map<Integer, Integer> map = new HashMap<>();

        for (int i=0; i<n; i++) {
            int tmp = sc.nextInt();
            if (map.containsKey(tmp)) {
                map.put(tmp, map.get(tmp)+1);
            } else {
                map.put(tmp, 1);
            }
        }

//        System.out.println(map);

        Set<Integer> set = map.keySet();
        List<Integer> list2 = new ArrayList<>();
        List<Integer> list4 = new ArrayList<>();

        for (int t: set) {
            if (map.get(t) >= 2) list2.add(t);
            if (map.get(t) >= 4) list4.add(t);

        }

//        Collections.reverse(list2);
//        Collections.reverse(list4);

        Collections.sort(list2, Collections.reverseOrder());
        Collections.sort(list4, Collections.reverseOrder());
//        System.out.println(list2);
//        System.out.println(list4);


        System.out.println(Math.max((list2.size() < 2) ? 0 : (long)list2.get(0) * (long)list2.get(1), (list4.size() < 1) ? 0 : (long)list4.get(0) * (long)list4.get(0)));

    }

}

