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
def judge(lst):
	x = 0
	y = 0
	memo = 0
	for i in range(0, len(lst)-1):
		if lst[i] == lst[i+1]:
			x = lst[i]
			memo = i
			break
	for i in range(memo+2, len(lst)-1):
		if lst[i] == lst[i+1]:
			y = lst[i]
			break
	return x*y

N = int(raw_input())
A = map(int, raw_input().split())
A.sort(reverse=True)

print judge(A)