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

temp_set=set()

l = []

for a in A:
  if a in temp_set:
    l.append(a)
    temp_set.remove(a)
  else:
    temp_set.add(a)
    
l.sort()
if len(l)>=2:
  print(l[-2]*l[-1])
else:
  print(0)