While playing with geometric figures Alex has accidentally invented a concept of a $n$-th order rhombus in a cell grid.

A $1$-st order rhombus is just a square $1 \times 1$ (i.e just a cell).

A $n$-th order rhombus for all $n \geq 2$ one obtains from a $n-1$-th order rhombus adding all cells which have a common side with it to it (look at the picture to understand it better).

[Image]

Alex asks you to compute the number of cells in a $n$-th order rhombus.

-----Input-----

The first and only input line contains integer $n$ ($1 \leq n \leq 100$) — order of a rhombus whose numbers of cells should be computed.

-----Output-----

Print exactly one integer — the number of cells in a $n$-th order rhombus.

-----Examples-----

Input 1

Output 1 Input 2

Output 5 Input 3

Output 13

-----Note-----

Images of rhombus corresponding to the examples are given in the statement.