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())
a=[int(x) for x in input().split()]
a.sort()
lar=sec=i=0
while(i<n-1):
    if a[i]==a[i+1]:
        i+=1
        if a[i]>lar:
            sec=lar
            lar=a[i]
        elif a[i]>sec:
             sec=a[i]
    i+=1
print(lar*sec)
    
