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.*;

class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        Map<Long, Integer> map = new HashMap<>();

        for (int i = 0; i < N; i++) {
            long value = sc.nextLong();
            if (map.containsKey(value)) {
                map.put(value, map.get(value) + 1);
            } else {
                map.put(value, 1);
            }
        }

        List<Long> candidates = new ArrayList<>();
        for (Map.Entry<Long, Integer> entry : map.entrySet()) {
            if (entry.getValue() >= 4) {
                candidates.add(entry.getKey());
                candidates.add(entry.getKey());
            } else if (entry.getValue() >= 2) {
                candidates.add(entry.getKey());
            }
        }
        Collections.sort(candidates);

        if (candidates.size() >= 2) {
            long a = candidates.get(candidates.size() - 1);
            long b = candidates.get(candidates.size() - 2);
            System.out.println(a * b);
        } else {
            System.out.println(0);
        }
    }
}