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
from collections import Counter
n,*a=map(int,open(0).read().split())
b=[i for i in Counter(a).items() if i[1]>1]
b.sort()
c=[0]
for i in b[::-1]:
    if i[1]>=4:
        c.append(i[0]**2)
if len(b)>=2:
    c.append(b[-1][0]*b[-2][0])
print(max(c))