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: Wrong Answer)

import collections
import sys
n = int(input())
ls = list(map(int,input().split()))
c =collections.Counter(ls)
d = list(c)
p = []
if c[d[0]] < 2:
    print(0)
    sys.exit()
if c[d[1]] < 2:
    print(0)
    sys.exit()
for i in range(len(d)):
    if c[d[i]] >1:
        p.append(d[i])
mx1 = max(p)
p.remove(mx1)
mx2 = max(p)
print(mx1 * mx2)