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)

#ARc081C
import sys

n=int(raw_input())
l=map(int,raw_input().split())
l1=sorted(l,reverse=True)
l2=[]
for i in xrange(n-1):
 if l1[i]==l1[i+1]:
  l2.append(l1[i])
if len(l2)<2:
 print 0
 sys.exit()
ls=list(set(l2))
if l1.count(ls[-1])>3:
 res=ls[-1]**2
else:
 res=ls[-1]*ls[-2]
print res