n,k=map(int,input().split())
a=0
for i in range(1<<n):
	l=[j for j in range(n) if (i>>j)&1==1]
	r=[j for j in range(n) if (i>>j)&1==0]
	a+=l[0]==k-1 and l[-1]>r[0]
print(a)