While playing with geometric figures Alex has accidentally invented a concept of a nn-th order rhombus in a cell grid.
A 11-st order rhombus is just a square 1×11×1 (i.e just a cell).
A nn-th order rhombus for all n≥2n≥2 one obtains from a n−1n−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 nn-th order rhombus.
The first and only input line contains integer nn (1≤n≤1001≤n≤100) — order of a rhombus whose numbers of cells should be computed.
Print exactly one integer — the number of cells in a nn-th order rhombus.
1
1
2
5
3
13
Images of rhombus corresponding to the examples are given in the statement.
算格子數
就是等差數列 1 + 3 + 5 + ....
最後一塊 last = n * 2 -1; 這個會重複
class Program { static void Main(string[] args) { Console.WriteLine(Solution.Compute(Convert.ToInt32(Console.ReadLine()))); } } class Solution { public static int Compute(int n) { int last = n * 2 - 1; return (1 + last) * n - last; } }