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: Runtime Error)

# -*- coding:utf-8 -*-

N = int(input())
A = map(int,input().split())
A = sorted(A,reverse=True)

i = 0
check = 0
x = 0
y = 0

while(i<=N and check == 0):
    count = A.count(A[i])
    if(count>=4):
        x = A[i]
        y = A[i]
        check = 1
    elif(count>=2):
        if(x == 0):
            x = A[i]
            i = i + count
        else:
            y = A[i]
            check = 1
    else:
        i = i + count

if(check == 0):
    print("0")
else:
    print(x*y)