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 Julia (0.5.0) (judge verdict: Wrong Answer)

function main()
  
  N = parse(Int,readline())
  A = map(x -> parse(Int,x), split(readline()))
  
  sort!(A,rev = true)
  
  count = 0
  check = 0
  count2 = 0
  ans = 0
  
  for i in 1:N
    
    if check != A[i]
      check = A[i]
      count = 1
    else
      count += 1
    end
    
    if count == 2
      if ans == 0
        ans = 1
      end
      ans *= A[i]
      count2 += 1
    end
    
    if count2 == 2
      break
    end
    
  end
  
  if count2 == 2
    println(ans)
  else
    println(0)
  end
  
end

main()