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.HashMap;
import java.util.Scanner;

public class Main {
    private static Scanner sc;

    public Main() {
    }

    public static void main(String[] args) {
        sc = new Scanner(System.in);
        new Main().solve();

    }

    private void solve() {
        int N = sc.nextInt();
        int[] bars = new int[N];

        for (int i = 0; i < N; i++) {
            bars[i] = sc.nextInt();

        }

        Arrays.sort(bars);
        HashMap<Integer, Integer> dic = new HashMap<Integer, Integer>();
        long a = 0;
        long b = 0;
        for (int i = N - 1; i >= 0; i--) {
            int num = bars[i];
            if (dic.containsKey(num)) {
                dic.put(num, dic.get(num) + 1);
                if (dic.get(num) >= 2) {
                    if (a == 0) {
                        a = num;
                    } else {
                        b = num;
                    }
                    dic.put(num, 0);
                }
                if (a != 0 && b != 0) {
                    break;
                }
            } else {
                dic.put(num, 1);
            }
        }
        System.out.println(a * b);
    }
}

