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.Arrays;
import java.util.Collections;
import java.util.Scanner;

public class Main {

  public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);

    int n = Integer.parseInt(sc.next());
    Integer[] a = new Integer[n];

    for (int i = 0; i < n; i++) {
      a[i] = Integer.parseInt(sc.next());
    }
    Arrays.sort(a, Collections.reverseOrder());

    int count = 0;
    long sq = 1;

    for (int i = 1; i < n; i++) {
      if (a[i].equals(a[i - 1])) {
        sq *= a[i];
        i++;
        count++;
        if (count >= 2) {
          break;
        }
      }
    }

    if (count < 2) {
      System.out.println(0);
    } else {
      System.out.println(sq);
    }
    sc.close();
  }
}