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
N = int(input())						# 5
a = [int(i) for i in input().split()]	# 1 2 3 4 5 ...


a.sort(reverse=True)

s=0
t=0
x=0
y=0
for _ in range(N):
	i = a[_]
	if t==0:
		if(s==i):
			t = i
		else:
			s = i
	else:
		if(x==i):
			y = i
			break
		else:
			x = i


print(s * x)

