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 void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		
		long[] map = new long[N];
		for (int i = 0; i < N; i++) {
			map[i] = sc.nextLong();
		}
		
		Arrays.sort(map);
		
		long a = 0;
		for (int i = map.length - 1; i > 0; i--) {
			if (map[i] == map[i - 1]) {
				a = map[i];
				map[i] = -1;
				map[i - 1] = -2;
				break;
			}
		}
		
		Arrays.sort(map);
		
		long b = 0;
		for (int i = map.length - 1; i > 0; i--) {
			if (map[i] == map[i - 1]) {
				b = map[i];
				break;
			}
		}
		
		long ans = a * b;
		System.out.println(ans);
	}
}