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 = sorted(list(map(int, input().split())),reverse=True)
x, y = 0, 0
for i in range(N-1):
    if A[i] == A[i+1]:
        x = A[i]
        break
for j in range(i+2,N-1):
    if A[j] == A[j+1]:
        y = A[j]
        break
print(x*y)