# coding: utf-8

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

def move(mv):
    cnt = int(abs(mv)/l)
    if (mv % l != 0):
        cnt += 1
    return cnt

ans = 0
if (y > 0):
    ans += move(y)
    if(x != 0):
        ans += move(x)
        ans += 1
elif (y < 0):
    ans = move(y)
    ans += 2
    move(x)
else:
    ans += 1
    move(x)
print(ans)