House of Cards
Input: Standard Input (stdin)
Output: Standard Output (stdout)
Memory limit: 100 megabytes
Time limit: 1.0 seconds
Output: Standard Output (stdout)
Memory limit: 100 megabytes
Time limit: 1.0 seconds
YĆ«ko and Mio are building a house of cards.
A house has N stories, where N is a whole number.
Each story is made out of struts, which may be supported by platforms.
 The top story has 2 struts and 1 platform.
 The secondtotop story has 4 struts and 2 platforms.
 The thirdtotop story has 6 struts and 3 platforms.
In general, each story has 2 more struts and 1 more platform than the story above it.
Note that the bottom story does not have a platform, because the table is already supporting it.
How many cards are needed to build a house with N stories?
Input
Input is an integer, 0 < N \le 10{,}000, which is the number of stories.
Output
Output an integer, K, the number of cards needed to build a house with N stories.
Example
This house has 4 stories. There are 2 + 4 + 6 + 8 = 20 struts and 1 + 2 + 3 = 6 platforms in this house.
This adds up to 20 + 6 = 26 cards.

Sample Input 1
4
Sample Output 1
26