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 *p*<sub class="lower-index">*i*</sub> = *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).
none
4 1
1
4 2
7
5 3
31
5 4
76
200 1
1
200 2
19901
200 3
2646701
200 4
584811251
400 1
1
400 2
79801
400 3
21253401
400 4
9477912501
600 1
1
600 2
179701
600 3
71820101
600 4
48187303751
800 1
1
800 2
319601
800 3
170346801
800 4
152620985001
1000 1
1
1000 2
499501
1000 3
332833501
1000 4
373086956251
4 4
24
def c(n, k):
	t=1; b=1
	for i in range(k):
		b*=(i+1)
		t*=(n-i)
	return t//b

def howmany(n, k):
	a=0; b=1; s=0
	for i in range(k+1):
		s+=b*c(n, i)
		buf=b
		b=i*(a+b)
		a=buf
	return s

def main():
	inp=input('').split(' ')
	n=int(inp[0]); k=int(inp[1])
	print(howmany(n,k))

if __name__=='__main__':
	main()