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 = input()
A = map(int, raw_input().split())

M = {}
for a in A:
  if a not in M:
    M[a] = 0
  M[a] += 1

V = [0, 0]
for a in M:
  if M[a]>=4:
    V += [a, a]
  elif M[a]>=2:
    V += [a]
V.sort()
print V[-1]*V[-2]
