#coding:utf-8

from math import ceil,fabs

X=float(input())
Y=float(input())
L=float(input())

if X==0 and Y!=0:
	print int(ceil(fabs(Y/L)))
elif X!=0 and Y==0:
	print int(ceil(fabs(X/L)))
elif X==Y==0:
	print 0
else:
	print int(ceil(fabs(Y/L))+ceil(fabs(X/L)))+1