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

public class Main {
	public static void main (String[] args) {
		// for C
		Scanner sc = new Scanner (System.in);
		int N = sc.nextInt ();
		long[] a = new long [N];
		int i;
		for (i=0; i<N; i++)
			a[i] = sc.nextLong ();
		Arrays.sort (a);
		long h=0, w=0;
		for (i=N-1; i>0; i--) {
			if (a[i]==a[i-1]) {
				h = a[i];
				i-=2;
				break;
			}
		}
		for (; i>0; i--) {
			if (a[i]==a[i-1]) {
				w = a[i];
				break;
			}
		}
		System.out.println (h*w);
	}
}