import math
X = int(input())
Y = int(input())
L = int(input())

Y_ziku = math.ceil(abs(Y) / L)
X_ziku = math.ceil(abs(X) / L)

if Y >= 1 and X == 0:
    print(Y_ziku)
elif Y >= 0:
    print(Y_ziku + X_ziku + 1)
elif Y < 0:
    print(Y_ziku + X_ziku + 2)
else:
    print(0)