x = int(input())
y = int(input())
l = int(input())
xd = 0
yd = 0
act = 0

while xd < abs(x):
    xd += l
    act += 1
while yd < abs(y):
    yd += l
    act += 1

if x == 0 and y >= 0:
    pass
elif y >= 0:
    act += 1
else:
    act += 2

print(act)