# wilcorec 
# Fig. 31.4 
# input: 41 5 30

def w(u,m,n):
  if u < 0:
    return 0
  elif (u == 0) or (m == 0) or (n == 0):
    return 1
  else:
    return w(u, m, n-1) + w(u-n, m-1, n)

u,m,n = map(int, input("u m n=? ").split())
print("count =", w(u, m, n))