X=gets.chomp.to_i
Y=gets.chomp.to_i
L=gets.chomp.to_i

def robot(x, y, distance)
  m = ((x - 0).abs.to_f / distance).ceil
  n = ((y - 0).abs.to_f / distance).ceil
  r = 0
  if m > 0 and n > 0
    r = 1
  end
  return m + n + r
end

puts robot(X, Y, L)