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())
As = list(map(int, input().split()))
As.sort(reverse=True)
rs = []
a = -1
for i in range(N):
  A = As[i]
  if A == a:
    rs.append(A)
    a = -1
  else:
    a = A
if len(rs) < 2:
  print(0)
  exit()
r = rs[0]*rs[1]
print(r)
