题目描述
The main building of the nation is developing complex patterns as each day progresses.
The task is to find the number of three sided closed figures on the nth day.
(Input – n
Output – number of triangles)
SAMPLE INPUT
2
SAMPLE OUTPUT
5
输入格式
见题面
输出格式
见题面
样例输入
2
SAMPLE
样例输出
5