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 num < 0:
			answer += 1
	
	print(answer)