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
import collections
n = int(raw_input())
sides = map(int, raw_input().split())
obj, squares, rectangles = collections.Counter(sides), list(), list()
for i in obj:
    if obj[i] >= 4:
        squares.append(i)
        rectangles.append(i)
    elif obj[i] >= 2:
        rectangles.append(i)
if (not rectangles and not squares) or (not squares and len(rectangles) < 2):
    print('0')
elif not squares and len(rectangles) >= 2:
    rectangles.sort(reverse=True)
    print(rectangles[0] * rectangles[1])
elif not rectangles and squares:
    squares.sort(reverse=True)
    print(squares[0] ** 2)
else:
    rectangles.sort(reverse=True)
    squares.sort(reverse=True)
    print(rectangles[0] * rectangles[1] if rectangles[0] * rectangles[1] > squares[0] ** 2 else squares[0] ** 2)
