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(raw_input())
a=map(int,raw_input().split())
b={}
for i in a :
    if i in b :
        b[i] += 1
    else :
        b[i] = 1
c = []
for i,j in b.items():
    if j>=2 :
        c.append(i)
    if j>=4 :
        c.append(i)
        
c=sorted(c)
if len(c) >= 2 :
    c = sorted(c)
    print c[-1]*c[-2]
else :
    print 0