from math import ceil
x=int(input())
y=int(input())
l=int(input())
ans=0
if y>=0:
    if x==0:
        print(ceil(y/l))
    elif abs(x)>0:
        print(ceil(y/l)+1+ceil(abs(x)/l))
else:
    print(2+ceil(abs(x)/l)+ceil(abs(y)/l))