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()))
from collections import Counter
a = Counter(a)
lis = []
 
for i,j in a.items():
    lis += [i]*(j//2)
 
#print(lis)
 
lis.sort(reverse=True)
if len(lis) <= 1:
    ans = 0
else:
    ans = lis[0]*lis[1]
 
print(ans)