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.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        try {
            // 標準入力
            InputStreamReader isr = new InputStreamReader(System.in);
            BufferedReader br = new BufferedReader(isr);
            int n = Integer.parseInt(br.readLine());
            String str[] = br.readLine().split(" ");
            long a[] = new long[n];
            for (int i = 0; i < n; i++) {
                a[i] = Long.parseLong(str[i]);
            }
            Arrays.sort(a);
            int i = n - 1;
            long x = -1;
            long y = -1;
            long before = -1;
            while (i >= 0) {
                long tmp = a[i];
                if (before == tmp) {
                    if (x == -1) {
                        x = tmp;
                        before = -1;
                    } else if (y == -1) {
                        y = tmp;
                        break;
                    }
                } else {
                    before = tmp;
                }
                i--;
            }
            if (x != -1 && y != -1) {
                System.out.println(x * y);
            } else {
                System.out.println(0);
            }
        } catch (IOException e) {
            e.printStackTrace();
           }
    }
}
