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

x_ti = abs(x) // l if x % l == 0 else abs(x) // l + 1
y_ti = abs(x) // l if y % l == 0 else abs(y) // l + 1
if y > 0:
    if x != 0:
        a = 1
else:
    a = 2

print(x_ti + y_ti + a)