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.Scanner;

class Main{


	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);			//文字の入力
		int N = sc.nextInt();
		long[] A = new long[N];

		for(int i = 0;i < N;i++){
			A[i] = sc.nextLong();
		}
		Arrays.sort(A);

		long one = 0;
		long sec = 0;
		for(int i = N-1;i>=1;i--){
			
			
			if(one == 0){
				if(A[i] == A[i-1]){
					one = A[i];
					i--;
				}
			}else{
				if(A[i] == A[i-1]){
					sec = A[i];
				}
			}
			
			
			if(one != 0 && sec != 0){
				System.out.println(one*sec);
				return;
			}
		}
		
		System.out.println(0);


	}
	

}