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.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] a = new int[n];
		for(int i =  0 ; i < n ; i++) a[i] = sc.nextInt();
		Arrays.sort(a);
		Map<Integer, Integer> map = new HashMap<Integer, Integer>();
		int x = -1;
		for(int i = n - 1 ; i >= 0; i--) {
			if(!map.containsKey(a[i])) {
				map.put(a[i], 1);
			}
			else {
				int j = i;
				for(j = i ; j >= 0 ; j--) {
					if(map.containsKey(a[j])) {
						map.put(a[j], map.get(a[j]) + 1);
					} else {
						break;
					}
				}
				if(x == -1 && map.get(a[i]) >= 4) {
					System.out.println(1L * a[i] * a[i]);
					return;
				} else if(x != -1 && x != a[i] && map.get(a[i]) >= 2) {
					System.out.println(1L * x * a[i]);
					return;
				} else if(map.get(a[i]) >= 2) {
					x = a[i];
				}
				i = j + 1;
			}
		}
		System.out.println(0);
	}
}