Ray Through Glasses

Suppose we put two panes of glass back-to-back. How many ways are there for light rays to pass through or be reflected after changing direction n times ? Following figure shows the situations when the value of n is 0, 1 and 2.
                                  

Input 

It is a set of lines with an integer n where 0 <= n <= 1000 in each of them.

Output 

For every one of these integers a line containing as described above.

Sample Input 

0
1
2

Sample Output 

1
2
3