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

Y_sei_ziku = math.ceil(Y / L)
X_sei_ziku = math.ceil(X / L)
Y_fu_ziku = math.ceil(Y // -1 / L)
X_fu_ziku = math.ceil(X // - 1 / L)

if Y >= 1 and X == 0:
    print(Y_sei_ziku)
elif Y >= 0 and X > 0:
    print(Y_sei_ziku + X_sei_ziku + 1)
elif Y >= 0 and X < 0:
    print(Y_sei_ziku + X_fu_ziku + 1)
elif Y < 0 and X >= 0:
    print(Y_fu_ziku + X_sei_ziku + 2)
elif Y < 0 and X >= 0:
    print(Y_fu_ziku + X_fu_ziku + 2)
else:
    print(0)