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 = input()
bars = map(int,raw_input().split(' '))
bars.sort()
h1_cand=0
h2_cand=0
h1=0
h2=0
for i in range(n):
  m = n-1-i
  if h1 > 0:
    if h2_cand == bars[m]:
      h2 = h2_cand
      break
    else:
      h2_cand = bars[m]
  else:
	if h1_cand == bars[m]:
    	  h1 = h1_cand
    	  h1_cand = 0
  	else:
    	  h1_cand = bars[m]
 
print h1*h2
