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 = input().split()

d = {}
for i in a:
    d[i] = d.get(i,0)+1
    
for i in d:
    d[i] = d[i]//2

s = []
for i in d:
    s += [int(i)]*int(d.get(i))
if(len(s)>=2):
    s.sort()
    print(s[-1]*s[-2])
else:
    print(0)