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.Scanner;

public class Main {

	public static long rectangle(int a[]) {
		long s;
		int height = 0, len = 0;
		int n = a.length;

		for (int i = n - 1; i > 0; --i) {
			if (a[i] == a[i - 1]) {
				if (len == 0)
					len = a[i];
				else {
					if (height == 0)
						height = a[i];
					else
						break;
				}
				--i;
			}
		}

		s = (long) len * (long) height;
		return s;
	}

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n, a[];

		n = sc.nextInt();
		a = new int[n];
		for (int i = 0; i < n; ++i)
			a[i] = sc.nextInt();

		sc.close();

		Arrays.sort(a);
		long ans = rectangle(a);

		System.out.println(ans);
	}

}
