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()
lens=raw_input().split()
lens=[int(x) for x in lens]
lens.sort()
lens=lens[::-1]
i=0
needed=[]
while i<n-1:
    if lens[i] == lens[i+1]:
        needed.append(lens[i])
        i+=1
    i+=1
if len(needed)<2:print '0'
else: print needed[0]*needed[1]
        