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

        int n = sc.nextInt();
        long[] a = new long[n];
        HashMap<Long,Long> map = new HashMap<>();
        for(int i = 0; i<n; i++) {
            a[i] = sc.nextLong();

            map.putIfAbsent(a[i],0L);
            map.put(a[i], map.get(a[i])+1L);
        }

        Arrays.sort(a);
        //for(long i:a) System.out.println(i+" "+map.get(i));

        for(int k = n-1; k>=0; k--) {
            //System.out.println(a[k]+" "+map.get(a[k]));
            if (map.get(a[k]) >= 4) {
                System.out.println(a[k] * a[k]);
                return;
            } else if (map.get(a[k]) >= 2) {
                for (int i = k; i >= 0; i--) {
                    if ((a[i] != a[k]) && (map.get(a[i]) >= 2)) {

                        //System.out.println(a[i]+" "+a[k] +" "+((long)a[i]==(long)a[k]));
                        System.out.println(a[k]*a[i]);
                        return;
                    }
                }

            }
        }
        System.out.println(0);

    }
}
