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();
    Map<Integer, Integer> map = new HashMap<>();
    for (int i = 0; i < N; i++) {
      int a = sc.nextInt();
      map.put(a, map.getOrDefault(a, 0) + 1);
    }
    
    PriorityQueue<Integer> pq = new PriorityQueue<>(Collections.reverseOrder());
    for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
      if (entry.getValue() >= 4) {
        pq.offer(entry.getKey());
        pq.offer(entry.getKey());
      } else if (entry.getValue() >= 2) {
        pq.offer(entry.getKey());
      }
    }
    
    if (pq.size() >= 2) {
      int a = pq.poll();
      int b = pq.poll();
      System.out.println((long)a*b);
    } else {
      System.out.println(0);
    }
  }
}