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.math.BigDecimal;
import java.util.Arrays;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		sc.nextLine();
		int[] array = new int[n];
		for (int i = 0; i < n; i++) {
			array[i] = sc.nextInt();
		}
		sc.close();
		Arrays.sort(array);
		int count1 = 1;
		int count2 = 0;
		int width = array[n - 1];
		int height = 0;
		boolean widthFixed = false;
		boolean heightFixed = false;
		for (int i = n - 2; i >= 0; i--) {
			if (!widthFixed) {
				if (array[i] == width) {
					count1++;
					if (count1 == 4) {
						height = width;
						widthFixed = true;
						heightFixed = true;
						break;
					}
				} else {
					if (count1 < 4 && count1 >= 2) {
						count1 = 2;
						widthFixed = true;
						height = array[i];
						count2 = 1;
					} else {
						count1 = 1;
						width = array[i];
					}
				}
			} else {
				if (array[i] == height) {
					count2++;
					if (count2 == 2) {
						heightFixed = true;
						break;
					}
				} else {
					if (count2 < 2) {
						height = array[i];
						count2 = 1;
					}
				}
			}
		}
		if (heightFixed && widthFixed) {
			BigDecimal mupti = new BigDecimal(width).multiply(new BigDecimal(height));
			System.out.println(mupti);
		} else {
			System.out.println(0);
		}
		
	}
}