After finishing his 1047 assignment, Parsa has developed a deep hatred for all rectangular shapes (thanks to his LCD being a rectangle). So, he decides to turn everything into triangles.

He starts with a stick of length n and wants to cut it twice into three smaller sticks of positive integer lengths. Then, he tries to form a triangle using those three pieces.

Now Parsa wonders, how many different triangles can he make by cutting the stick of length n into three positive integers that form a valid triangle?

Two triangles are considered different if the sets of side lengths are different (regardless of order).

Input Format:

The first line an integer n.

Output:

Output the number of different triangles.

Sample Input:

12

Sample Output:

3