x = int(input())
y = int(input())
l = int(input())
if x == 0 and y == 0:
    print(0)
    exit()
if x >= 0:
    ans += -(-x//l) -(-abs(y)//l) + 1
elif x < 0:
    ans += -(-abs(x)//l) -(-abs(y)//l) + 2
print(ans)