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
import sys

N=input()
#print N
A=list(map(int,raw_input().split()))
A.sort()
#print A

hen=[]
tmp_hen=-1
for i in reversed(A):
	if len(hen)==2:
		break
	if tmp_hen==i:
		hen.append(i)
		tmp_hen=-1
	else:
		tmp_hen=i


if len(hen)<2:
	print 0
else:
	print hen[0]*hen[1]

