x = int(input())
y = int(input())
l = int(input())

#方向転換
step = 2
if y>=0: step -= 1
if x==0 and y>0: step -= 1
if x==0 and y==0: step = 0

#真っ直ぐ
step += abs(int(x/l)) + abs(int(y/l))
if x%l>0: step += 1
if y%l>0:	step += 1

print(step)