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())
tmp = raw_input()

As = [int(a) for a in tmp.split()]

dic = {}
maxes = [0, 0]
for a in As:
    if a not in dic:
        dic[a] = 0
    dic[a] += 1
    if dic[a] % 2 == 0:
        if maxes[0] < a:
            maxes[0], maxes[1] = a, maxes[0]
        elif maxes[1] < a:
                maxes[1] = a

print (maxes[0] * maxes[1])