Star
题目描述
B. Star
time limit per test
2 secondsmemory limit per test
256 megabytesinput
standard inputoutput
standard output
Input
The input contains a single integer a (1≤a≤18257).
Output
Print a single integer output (1≤output≤2·109).
Examples
Input
2
Output
13
题目来源：fps-www.educg.net-codeforce-1-2833.xml.zip；FPS 共享题包，题包内第 2574 题。保留原作者与原赛事署名。