302438: CF470A. Crystal Ball Sequence

Memory Limit：256 MB Time Limit：2 S
Judge Style：Text Compare Creator：
Submit：0 Solved：0

Description

A. Crystal Ball Sequencetime limit per test2 secondsmemory limit per test256 megabytesinputstandard inputoutputstandard output

Crystal ball sequence on hexagonal lattice is defined as follows: n-th element is the number of lattice points inside a hexagon with (n + 1) points on each side. The formula is Hn = 3·n·(n + 1) + 1. You are given n; calculate n-th element of the sequence.

Input

The only line of input contains an integer n (0 ≤ n ≤ 9).

Output

Output the n-th element of crystal ball sequence.

ExamplesInput
1
Output
7
Input
3
Output
37

Input

Source/Category

加入题单

上一题 下一题 算法标签：