Matrix = [[0]*110 for i in range(110)]
def f(N,M):
global Matrix
if(Matrix[N][M]):
return Matrix[N][M]
elif N==M or M==0:
return 1
elif N<M:
Matrix[N][M]=0
return Matrix[N][M]
elif M==1:
Matrix[N][M]=N
return Matrix[N][M]
else:
Matrix[N][M]=f(N-1,M)+f(N-1,M-1)
return Matrix[N][M]
n,m=map(int,input().split(" "))
print(f(n,m))