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

d = collections.Counter(A)

x = sorted([i for i in d.items() if i[1]>1])
if len(x)==0 :
  print(0)
elif x[-1][1] >3 :
  print(x[-1][0]**2)
elif len(x) == 1 :
  print(0)
else:
  print(x[-1][0]*x[-2][0])