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())
d={}

for i in input().split():
	x=int(i)
	if x not in d:d[x]=1
	else:d[x]+=1

cnt=0
ans=1
for t in sorted(d.items(),reverse=True):
	if t[1]>=2:
		ans*=t[0]
		cnt+=1
	if cnt==1 and t[1]>=4:
		ans*=t[0]
		cnt+=1
	if cnt>=2:
		break

print(ans if cnt>=2 else 0)