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,*a=map(int,sys.stdin.read().split())

a.sort(reverse=True)
c=0
f=0
ans=[]
for i in range(n-1):
  if a[i]==a[i+1]:
    c+=1
    f+=1
    ans.append(a[i])
  else:
    f=0
  if (c>1 and f==1) or (c>2 and f==3):
    print(ans[0]*ans[-1])
    sys.exit()
print(0)
  
  
