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)

lst = []
N = int(input("Enter number of elements : "))
for i in range(0,N):
    lst.append(int(input()))
temp = [x for x in lst if lst.count(x)>1]
list_set = set(temp)
dups = (list(list_set))
if (len(dups)<2):
   print('0')
   print('No rectangle can be formed')
else:
    a = dups[0]; b = dups[1]
    n=len(dups)    
    for i in range(0, n):
      for j in range(i + 1, n):
        if (dups[i]*dups[j]>a*b):
             a = dups[i]
             b = dups[j]
    print(a*b)
    print(a,' times ',b,' rectangle can be formed')