from math import ceil


def main():
    X = int(input())
    Y = int(input())
    L = int(input())

    if Y < 0:
        move_num = 2
    elif X != 0:
        move_num = 1
    else:
        move_num = 0

    move_num += ceil(abs(Y / L))
    move_num += ceil(abs(X / L))
    print(move_num)


if __name__ == "__main__":
    main()