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.*;
import java.lang.*;
 
 //O(100000000)
public class Main {
    public static void main(String[] args) {

        Scanner sc  = new Scanner(System.in);
        long N = Long.parseLong(sc.next());

        long[] dp  = new long[(int)N+1];
        for(int i=0;i<N;i++){
            dp[i] = Long.parseLong(sc.next());
        }
        
        Arrays.sort(dp);
        long a = 0;
        long b = 0;
        
        for(int i = dp.length-1; i  >= 1 ; i-- ){
            
            if(i>3){
                
                if(dp[i]==dp[i-3]&&dp[i]>a)
                a = b = dp[i];
                
            }
            
            if(dp[i] == dp[i-1]&&dp[i]>a){
                a = dp[i];
            }
            
            if(dp[i] == dp[i-1]&&a!=0&&a!=dp[i]){
                if(dp[i]>b)b = dp[i];
            }
       
        }
        
  
        System.out.print(a*b);
        System.out.println();
    }

}