# wiliter1 
# Fig. 31.5 
# input: 41 5 30

u,m,n = map(int, input("u m n=? ").split())
# w[z][x][y]
w = [[[0 for y in range(n+1)] 
       for x in range(m+1)] for z in range(u+1)]
for z in range(u+1):
  for x in range(m+1):
    w[z][x][0] = 1
for z in range(u+1):
  for y in range(n+1):
    w[z][0][y] = 1
for x in range(m+1):
  for y in range(n+1):
    w[0][x][y] = 1
for x in range(1,m+1):
  for y in range(1,n+1):
    for z in range(1,u+1):
      if z < y:
        w[z][x][y] = w[z][x][y-1]
      else:
        w[z][x][y] = w[z][x][y-1] + w[z-y][x-1][y]
print("w =", w[u][m][n])