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.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine());
        HashMap<Integer, Integer>map = new HashMap<>();
        StringTokenizer st = new StringTokenizer(br.readLine());
        for(int i = 0;i < n;i++){
            int a = Integer.parseInt(st.nextToken());
            if(map.containsKey(a))
                map.put(a, map.get(a) + 1);
            else map.put(a, 1);
        }
        long ans = 0;
        int max1 = 0, max2 = 0;
        for(Integer key : map.keySet()){
            int val = map.get(key);
            //System.out.println(key + " " + val);
            if(val >= 4){
                ans = Math.max(ans, key*1L*key);
            }
            if(val >= 2){
                //System.out.println(max1 + " " + max2);
                if(key > max1){
                    max2 = max1;
                    max1 = key;
                }
                else if(key > max2){
                    max2 = key;
                }
                //System.out.println(max1 + " " + max2);
            }
        }
        //System.out.println(max1 + " " + max2);
        ans = Math.max(ans, max1*1L*max2);
        System.out.println(ans);
    }
}
