How Many?#3260
You have a collection of different books, and you want to pack of them to take on a trip. In how many ways can you select books from the available?
The input consists of two integers, (1 \le n \le 12) — the total number of books, and (0 \le k \le n) — the number of books you want to take with you.
Print the number of ways to choose books from .
Ejemplo 1
Ejemplo 2