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 in = new Scanner(System.in);
        int N = in.nextInt();
        long A[] = new long[N];
        long ans = 0;
        long ans2 = 0;
        Arrays.fill(A, 0);

        for(int cnt = 0; cnt < N; cnt++){
        	A[cnt] = in.nextLong();
        }

        Arrays.sort(A);

        for(int cnt = N - 1; cnt > 0; cnt--){
        	if(A[cnt] == A[cnt-1]){
        		if(A[cnt] > ans){
        			ans = A[cnt];
        			cnt--;
        		}
        		else if(A[cnt] > ans2){
        			ans2 = A[cnt];
        			cnt--;
        		}
        	}
        }
        System.out.println(ans * ans2);

    }
}