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 (3.4.3) (judge verdict: Runtime Error)

line1 = 0
line2 = 0

n = int(input())

lines = list(map(int,input().split()))
lines.sort()

mx1,mx2 = 0,0
temp = 0
streak = 0
for l in lines:
  if l != temp:
    temp = l
    streak = 0
  elif l == temp and streak = 0:
    streak += 1
  elif l == temp and streak == 1 and l > mx1:
    mx2 = mx1
    mx1 = l
    streak = 0
  elif l == temp and streak == 1 and l > mx2:
    mx2 = l
    streak = 0
print(mx1 * mx2)