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 PyPy3 (2.4.0) (judge verdict: Runtime Error)

n=int(input())
data=[int(aa) for aa in input().split()]
d=[0 for aa in range(100000+1)]
for aa in data:
    d[aa]+=1
#print(d)
mydata=0
mylist=[0,0]
for aa in range(100000+1):
    if d[aa] >3:
        mydata=aa
    if d[aa] >1 :
        if aa not in mylist:
            mylist.pop(0)
            mylist.append(aa)
#            print(mylist)
 
print(max(mydata*mydata,mylist[0]*mylist[1]))
n=int(input())
data=[int(aa) for aa in input().split()]
d=[0 for aa in range(100000+1)]
for aa in data:
    d[aa]+=1
#print(d)
mydata=0
mylist=[0,0]
for aa in range(100000+1):
    if d[aa] >3:
        mydata=aa
    if d[aa] >1 :
        if aa not in mylist:
            mylist.pop(0)
            mylist.append(aa)
#            print(mylist)

print(max(mydata*mydata,mylist[0]*mylist[1]))