Problem:
Score : 300 points

Problem Statement

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.

Sample Input 1

6
3 1 2 4 2 1

Sample Output 1

2

1 \times 2 rectangle can be formed.

Sample Input 2

4
1 2 3 4

Sample Output 2

0

No rectangle can be formed.

Sample Input 3

10
3 3 3 3 4 4 4 5 5 5

Sample Output 3

20

Solution in Python (2.7.6) (judge verdict: Wrong Answer)

n = input()

a = map(int, raw_input().split())
a.sort(reverse = True)
a.append(0)
tmp = [0]
ct = 0

key = a.pop(0)
for i in range(len(a) - 1):
    if a[i] == a[i + 1]:
        tmp.append(a[i])
        i += 2
        if len(tmp) == 3:
            break

if len(tmp) < 3:
    print 0
else:
    print tmp[1] * tmp[2]