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

X = int(x)
Y = int(y)
L = int(l)

a = -( (-abs(X)) // L)
b = -( (-abs(Y)) // L)

if Y >= 0:
    if X != 0:
        c = a + b + 1
    else:
        c = a + b
else:
    c = a + b + 2
print(c)