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.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;


public class Main {

	/**
	 * @param args
	 * @throws IOException 
	 */
	public static void main(String[] args) throws IOException {
		// TODO Auto-generated method stub
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		br.readLine();
		
		String[] tmpArray = br.readLine().split(" ");
		int[] sticks = new int[tmpArray.length];
		for(int i = 0; i < tmpArray.length ; i++){
			sticks[i] = Integer.parseInt(tmpArray[i]);
		}
		
		System.out.println(makeRectangle(sticks));
	}
	
	static long makeRectangle(int[] sticks){
		Arrays.sort(sticks);
		int a = 0;
		int b = 0;
		int prev = -1;
		
		for(int i = sticks.length - 1; i >= 0 ; i-- ){
			if(prev == sticks[i]){
				if(a == 0){
					a = sticks[i];
					prev = -1;
					continue;
				}
				else {
					b = sticks[i];
					break;
				}
			}
			
			prev = sticks[i];
		}
		
		return (long)a*b;
	}

}
