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;

/**
 * http://abc071.contest.atcoder.jp/tasks/arc081_a
 */
public class Main {
	
	public static void main(String[] args) {
		
		Scanner sc = new Scanner(System.in);
		final int N = sc.nextInt();
		long[] a = new long[N];
		for(int i=0; i<N; i++){
			a[i] = sc.nextLong();
		}
		sc.close();
		
		Arrays.sort(a);
		long max = 0;
		for(int i=N-1; i>0; i--){
			if(a[i]==a[i-1]){
				max = a[i];
				a[i]= -1;
				a[i-1] = -1;
				break;
			}
		}
		
		Arrays.sort(a);
		long max2 = 0;
		for(int i=N-1; i>0; i--){
			if(a[i]==a[i-1]){
				max2 = a[i];
				break;
			}
		}
		
		System.out.println(max*max2);

	}

}