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


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