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[] A = new long[N];
        for(int i = 0; i < N; i++) {
            A[i] = sc.nextLong();
        }
        sc.close();
        Arrays.sort(A);
        long[] K = new long[N];
        int index = 0;
        int index_k = 0;
        while(index < N-1){
            if(A[index] == A[index+1]){
                K[index_k++] = A[index];
                index += 2;
            }else{
                index++;
            }
        }
        Arrays.sort(K);
        long result = K[N-1] * K[N-2];
        System.out.println(result);

    }

}