题目描述
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.
Examples
Input
6
3 1 2 4 2 1
Output
2
Input
4
1 2 3 4
Output
0
Input
10
3 3 3 3 4 4 4 5 5 5
Output
20
输入格式
见题面
输出格式
见题面
样例输入
10
3 3 3 3 4 4 4 5 5 5
样例输出
20