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 scan = new Scanner(System.in);
		int n = Integer.parseInt(scan.next());scan.nextLine();
		int[] a = new int [n];
		for (int i = 0;i < n;++i){
			a[i] = Integer.parseInt(scan.next());
		}

		int count = 0;
		long ans = 0;
		Arrays.sort(a);
		for (int i =n-1;i>0; --i){
			if (count==2)break;
			if (a[i]==a[i-1]){
				++count;
				if (ans==0)ans=1;
				ans*=a[i];
				--i;
			}
		}
		if (count == 2){
			System.out.print(ans);
		}else{
			System.out.print(0);
		}


	}
}
//end
