x = int(input())
y = int(input())
l = int(input())
order_counter = 0

if y >= 0:
    order_counter += 1
    q, mod = divmod(abs(x), l)
    if mod == 0:
        order_counter += q
    else:
        order_counter += q + 1
else:
    order_counter += 2
    q, mod = divmod(abs(x), l)
    if mod == 0:
        order_counter += q
    else:
        order_counter += q + 1
print(order_counter)