def memoized_triple_step(step):
    """Find number of step combinations for maximum of three steps at a time

    :param step Number of steps left
    :return     Number of step combinations

    """
    if step < 0:
        return 0
    elif step == 0:
        return 1
    return memoized_triple_step(step - 3) + \
        memoized_triple_step(step - 2) + \
        memoized_triple_step(step - 1)