How Many?

Preparing for the calculus exam, Petya spread out $n$ different cheat sheets in front of himself. They were his salvation, as throughout the entire semester Petya had never bothered to properly study the material. There were so many cheat sheets that they didn’t fit into any pocket. Therefore, Petya decided to calculate the maximum number of cheat sheets he could take with him to the exam. And then the question arose: how many ways are there in total to choose the required number of cheat sheets?

Input

Contains the total number of cheat sheets $n(1\le n\le 12)$ and the number of cheat sheets $k(0\le k\le n)$ that Peter can take with him.

Output

Print the number of ways to choose $k$ cheat sheets from $n$.

Examples