Almost Identity Permutations
Description
A permutation p of size n is an array such that every integer from 1 to n occurs exactly once in this array.
Let's call a permutation an almost identity permutation iff there exist at least n - k indices i (1 ≤ i ≤ n) such that pi = i.
Your task is to count the number of almost identity permutations for given numbers n and k.
The first line contains two integers n and k (4 ≤ n ≤ 1000, 1 ≤ k ≤ 4).
Print the number of almost identity permutations for given n and k.
Input
The first line contains two integers n and k (4 ≤ n ≤ 1000, 1 ≤ k ≤ 4).
Output
Print the number of almost identity permutations for given n and k.
Samples
4 1
1
4 2
7
5 3
31
5 4
76