H. Triangles
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output

A regular triangle with a side equal to $$$n$$$ is drawn on a piece of paper. After that, the figure is divided into unit triangles, as shown in the figure for $$$n = 3$$$. How many different triangles can you find in this picture? Triangles are considered distinct if they differ either in size or location.

Input

The only line contains the integer $$$n$$$ ($$$1 \le n \le 10^4$$$).

Output

Print a single number — the number of distinct triangles.

Examples
Input
2
Output
5
Input
4
Output
27