# subs6-q13
# Section 6, Q.13, p.24, p.250
# inputs: 5 2

def c(n,s):
  if s == 0:
    return 1
  else:
    return c(n-1, s-1) * n//s

n, s = map(int, input("n s=? ").split())
print(c(n, s))