import math
x = int(input())
y = int(input())
l = int(input())
cnt = 0
if y >= 0:
    cnt += math.ceil(y/l)
elif y < 0:
    cnt += math.ceil(abs(y)/l) + 2
if x != 0:
    cnt += math.ceil(abs(x)/l) + 1
print(cnt)