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 sys
N = raw_input()
items = raw_input().split()
res = dict()
for i in items[:int(N)]:
    i = int(i)
    if res.get(i) is None:
        res[i] = 1
    else:
        res[i] = res[i] + 1
long2 = [0,0]
for i, num in res.iteritems():
    if num < 2:
        continue
    if i > long2[0]:
        if num >= 4:
            long2 = [i, i]
        else:
            long2 = [i, long2[0]]
    elif i > long2[1]:
        long2[1] = i
print long2[0] * long2[1]