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
a  =  int(input())

b = list(map(int,input().split()))

b.sort()

c = 1
d = 0
dd = 0

p = b[0]

for i in range(1,a):
	if p == b[i]:
		c += 1
	elif p != b[i]:
		p = b[i]
		c = 1
	if c == 2:
		d = dd
		dd = p
	elif c == 4:
		d = p
		dd = p

print(d*dd)