CF1180A.Alex and a Rhombus

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).

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

亚历克斯在摆弄几何图形时，偶然在方格纸上发明了一种“$n$阶菱形”的概念。

一个 $1$ 阶菱形就是一个 $1 \times 1$ 的正方形（即仅一个方格）。

对任意 $n \geq 2$，$n$ 阶菱形由 $(n-1)$ 阶菱形通过添加所有与它有公共边的方格而得到（参见下图以更直观地理解）。

亚历克斯请你计算一个 $n$ 阶菱形所包含的方格数量。

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.

第一行且唯一的一行输入包含一个整数 $n$（$1 \leq n \leq 100$）——表示需要计算其格子数量的菱形的阶数。

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

输出一个整数——第 $n$ 阶菱形中的格子数量。

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

示例对应的菱形图像在题目描述中给出。