import math
X = abs(int(input()))
Y = int(input())
L = int(input())
cnt = 0

if Y >= 0:
    cnt += math.ceil(Y/L)
    if X > 0:
        cnt += math.ceil(X/L) + 1

elif X > 0:
    cnt += math.ceil(X/L) + 1
    if Y < 0:
        cnt += math.ceil(abs(Y)/L) + 1

elif Y < 0:
    cnt += math.ceil(abs(Y)/L) + 2

print(int(cnt))