shape Area

Below we will define an n-interesting polygon. Your task is to find the area of a polygon for a given n.

A 1-interesting polygon is just a square with a side of length 1. An n-interesting polygon is obtained by taking the n - 1-interesting polygon and appending 1-interesting polygons to its rim, side by side. You can see the 1-, 2-, 3– and 4-interesting polygons in the picture below.

Example

• For n = 2, the output should be
  solution(n) = 5;
• For n = 3, the output should be
  solution(n) = 13.

Input/Output

• [execution time limit] 4 seconds (py3)
• [input] integer nGuaranteed constraints:
  1 ≤ n < 104.
• [output] integerThe area of the n-interesting polygon.