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 Ruby (2.3.3) (judge verdict: Wrong Answer)

# cook your code here
n = gets.to_i     

a = gets.split.map { |x| x.to_i }   

a = a.sort
a = a.reverse 
flag = 0
mul = 1  

while flag<2 and a.size>0
    x = a.count(a[0])
    if x>3 
        flag=2;
        mul = a[0]*a[0];
    elsif x>1        
        flag += 1         
        mul *= a[0]
    end     
    a.delete(a[0])
end 

if flag<2  
    puts "0"      
else       
    puts mul  
end