x=gets.to_i
y=gets.to_i
distance=gets.to_f
order=0

def custom_round(num)
  if num < 1
    return 1
  else
    return num.floor
  end
end

if x == 0 && y == 0
  puts order
elsif y == 0 && x > 0
  order += 1
  puts order + custom_round(x / distance)
elsif y == 0 && x < 0
  order += 1
  puts order + custom_round(x.abs / distance)
elsif x == 0 && y > 0
  puts order + custom_round(y / distance)
elsif x == 0 && y < 0
  order += 2
  puts order + custom_round(y.abs / distance)
elsif x > 0 && y > 0
  order += 1
  puts order + custom_round(x / distance) + custom_round(y / distance)
elsif x < 0 && y > 0
  order += 2
  puts order + custom_round(x.abs / distance) + custom_round(y / distance)
elsif x < 0 && y < 0
  order += 2
  puts order + custom_round(x.abs / distance) + custom_round(y.abs / distance)
elsif x > 0 && y < 0
  order += 2
  puts order + custom_round(x / distance) + custom_round(y.abs / distance)
end