from math import ceil

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

if X==Y==0:
    print(0)
elif (X==0 and Y>0):
    print(ceil(Y/L))
elif (X==0 and Y<0):
    print(ceil(abs(Y)/L)+2)
elif Y>=0:
    print(ceil(Y/L)+ceil(abs(X/L))+1)
else:
    print(ceil(abs(Y)/L)+ceil(abs(X/L))+2)