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
tree_dict = dict()

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

for x in l:
    if tree_dict.has_key(x):
        tree_dict[x] += 1
    else:
        tree_dict[x] = 1

long_line = 0
short_line = 0

for k,v in tree_dict.iteritems():
    if v >= 4:
        (_,_,short_line,long_line) = sorted((k,k,short_line,long_line))
        next
    if v >= 2:
        (_,short_line,long_line) = sorted((k,short_line,long_line))


print(long_line * short_line)
