X = int(input())
Y = int(input())
L = int(input())
i = 0

if Y < 0:
	i += 2
if X != 0:
	i += 1
i += +(X//L + Y//L)
if X%L != 0:
	i += 1
if Y%L != 0:
	i += 1
	
print(i)