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(a) for a in input().split()]

A.sort(reverse=True)
c1 = 0
c2 = 0
i = 1
while i < N:
    if A[i] == A[i-1]:
        if c1 == 0:
            c1 = A[i]
            i += 1
        else:
            c2 = A[i]
            break
    i += 1
    
print(c1*c2)