Score : $100$ points

Problem Statement

Two boys, A and B, will share $N$ indistinguishable sweets. How many ways are there to do this so that each boy gets a positive integer number of sweets?

Constraints

• $N$ is an integer.
• $1 \leq N \leq 15$

Input

Input is given from Standard Input in the following format:

$N$

Output

Print the answer as an integer.

2

1

There is only one way to share the sweets: A and B get one sweet each.

1

0

3

2