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 sc = new Scanner(System.in);
        int n = sc.nextInt();
        long[] a = new long[n];
        for(int i=0; i<n; i++){
            a[i] = sc.nextLong();
        }
        Arrays.sort(a);
        long side1 = 0;
        long side2 = 0;
        
        for(int i=n-1; i>0; i--){ //　i=0の時終了しないとa[i-1]を検証してしまう
            if(a[i] == a[i-1]){
                if(side1 == 0){
                    side1 = a[i];
                    i--;
                }else{
                    side2 = a[i];
                    break;
                }
            }
        }
        System.out.println(side1 * side2);
    }
}
