### Problem Statement

Given an equilateral triangle with side length N divided into a triangular grid of triangles with side length 1, count the total number of triangles present in the grid. For example, if N is 4:

```
/\
/__\
/\  /\
/__\/__\
/\  /\  /\
/__\/__\/__\
/\  /\  /\  /\
/__\/__\/__\/__\
```

Here there are ten right-side-up and six up-side-down triangles with a side length of 1, six right-side-up and one up-side-down triangles with a side length of 2, three right-side-up triangles with a side length of 3, and one right-side-up triangle with a side length of 4. The total number of triangles is 27.

### Definition

 Class: TriangleCount Method: count Parameters: int Returns: int Method signature: int count(int N) (be sure your method is public)

### Constraints

-N will be between 1 and 500, inclusive.

### Examples

0)

 `2`
`Returns: 5`
 There are four small triangles and one big triangle.
1)

 `4`
`Returns: 27`
 This is the example from the problem statement.
2)

 `100`
`Returns: 256275`

#### Problem url:

http://www.topcoder.com/stat?c=problem_statement&pm=2889

#### Problem stats url:

http://www.topcoder.com/tc?module=ProblemDetail&rd=5074&pm=2889

legakis

#### Testers:

lbackstrom , brett1479

Math