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

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