def get_number_aliens_x(ai_settings, alien_width):
    available_space_x = ai_settings.screen_width - 2 * alien_width
    number_aliens_x = int(available_space_x / (2 * alien_width))
    return number_aliens_x

def get_number_rows(ai_settigs, ship_height, alien_height):
    available_space_y = (ai_settigs.screen_height - (3 * alien_height) - ship_height)
    number_rows  = int (available_space_y / (3 * alien_height))
    return number_rows