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

1 \times 2 rectangle can be formed.

Sample Input 2

4
1 2 3 4

Sample Output 2

No rectangle can be formed.

Sample Input 3

10
3 3 3 3 4 4 4 5 5 5