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
# coding=utf-8

def count(list, target, num):
    l = len(list)
    c = 0
    for i in xrange(-num, l + 1):
        if list[-i] == target:
            c += 1
            if c == 4:
                return c
        else:
            return c
    return c


N = int(raw_input())
A = map(int, raw_input().split())

candidates = []
A.sort()
t = -1
for i in xrange(0, N + 1):
    n = count(A, A[t], t)
    for m in range(n / 2):
        candidates.append(A[t])
        if len(candidates) == 4:
            break
    t -= n
    if t < -N:
        break
if len(candidates) < 2:
    print 0
else:
    print candidates[0] * candidates[1]
