import math

def main():
	x = int(input())
	y = int(input())
	l = int(input())

	count = 0

	if(y < 0 and x != 0): #南方向に進む場合
		count += 1 
	elif(y < 0 and x == 0):
		count += 2

	count += math.ceil(abs(y) / l)


	if(x != 0):
		count += 1


	count += math.ceil(abs(x) / l)


	print(count)

if __name__ == '__main__':
	main()