if __name__ == "__main__":
	X = int(input())
	Y = int(input())
	L = int(input())
	
	answer = 0
	
	for num in [X, Y]:
		if num % L == 0:
			answer += abs(num) // L
		else:
			answer += abs(num) // L + 1
	
	if Y < 0:
		answer += 2
	elif X != 0:
		answer += 1
	
	print(answer)