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 (3.4.3) (judge verdict: Wrong Answer)

N=int(input())
A=list(map(str, input().split(' ')))
A.sort()
A.reverse()
a=0
b=0

for i in range(N):
    if A.count(A[i])>=4:
        print(int(A[i])**2)
        break
    elif A.count(A[i])>=2 and a==0:
        a=int(A[i])
        continue
    elif A.count(A[i])>=2 and a!=0:
        b=int(A[i])
        print(a*b)
        break
    else:
        continue
else:
    print(0)