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();
        }
        Arrays.sort(a);
        boolean first = false;
        boolean second = false;
        long firstNum = 0;
        long secondNum = 0;
        long tmp = a[0];
        int count = 1;
        for (int i = 1; i < n; i++) {
            if (tmp == a[i]) {
                count++;
                if (count % 2 == 1)
                    continue;
                if (!first && !second) {
                    firstNum = tmp;
                    first = true;
                } else if (first && !second) {
                    secondNum = tmp;
                    second = true;
                } else if (first && second) {
                    long x = secondNum;
                    secondNum = a[i];
                    firstNum = x;
                }
            } else {
                tmp = a[i];
                count = 1;
            }
        }
        long ans = firstNum * secondNum;
        System.out.println(ans);
    }
}