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=map(int, input().split())
a=sorted(a)[::-1]
k=-2
l=-2
for i in range(n-1):
    if (a[i]==a[i+1])&(i>k+1):
        if (k>=0):
            l=i
            break
        else:
            k=i
if l>=0:
    print(a[k]*a[l])
else:
    print(0)