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 collections
n = int(input())
a = [int(i) for i in input().split()]
x,y,z = collections.Counter(a),[0],[0,0]
for i in x.keys():
	if x[i]>=4:
		y.append(i)
	if x[i]>=2:
		z.append(i)
y,z = sorted(y),sorted(z)
print(max(y[-1]**2,z[-1]*z[-2]))