x, y, l = $stdin.read.split.map(&:to_i)
x = x.abs

count = 0
count += (y / l.to_f).ceil if y > 0 #北へ前進
count += 1 + (x / l.to_f).ceil if y < 0 || x > 0 #右1回転+東へ前進
count += 1 + (-y / l.to_f).ceil if y < 0 #右1回転+南へ前進
puts count