def BI(n,r):
	res=1
	for i in range(r):
		res*=n-i
		res=res//i+1
	return res
	
N=int(input())
M=int(input())
if M>N :
	print("0\n")
elif N==0 :
	print("1\n")
else :
	T=[0]*(M+1)
	for i in range(1,M+1):
		T[i]=1
		for j in range(N):
			T[i]*=j+1
		for j in range(i):
			T[i]-=T[j]*BI(i,j)
	print(T[M])