import math

X = int(input())
Y = int(input())
L = int(input())

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