x = int(input())
y = int(input())
l = int(input())
x = abs(x)
ans = 0
if y < 0:
    ans += 1
    x, y = -y, x
ans += (y + l - 1) // l + (0 if x == 0 else 1 + (x + l - 1) // l)
print(ans)