x = gets.chomp!.to_i.abs
y = gets.chomp!.to_i
l = gets.chomp!.to_i

inst = ((x + y.abs) / l)
inst += 1 if (x + y.abs) % l > 0
inst += 1 if x != 0 && y >= 0
inst += 2 if x == 0 && y < 0
inst += 2 if x != 0 && y < 0

puts inst