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 (3.8.2) (judge verdict: Wrong Answer)

n=int(input())
a=list(map(int,input().split()))
a.sort(reverse=True)
h1,h2,w1,w2=0,0,0,0
for i in range(n-3):
  h1,h2,w1,w2=a[i],a[i+1],a[i+2],a[i+3]
  if h1==h2 and w1==w2:
    break
  else:
    h1,h2,w1,w2,=0,0,0,0
print(h1*w1)