import math

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

def step(X, Y, L):
	count= 0
	
	if X != 0:
		count += 1
		count += math.ceil(abs(X)/L)
	
		if Y < 0:
			count += 2
			count += math.ceil(abs(Y)/L)	
		elif Y > 0:
			count += math.ceil(abs(Y)/L)
	return print (count)
	
step(X, Y, L)