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)

N = int(input())
a = list(map(int,(input().split())))
from collections import Counter
c = Counter(a)
L = []
LL = []
for k in c.keys():
    if c[k] >= 2:
        L.append(k)
    if c[k] >= 4:
        LL.append(k)
if LL:
    print((max(LL)**2))
else:
    if len(L) < 2:
        print(0)
    else:
        L.sort(reverse=True)
        print(L[0]*L[1])