def strategy_expensive(cookies, cps, history, time_left, build_info):
    """
    Always buy the most expensive item you can afford in the time left.
    """
    build_items_list = build_info.build_items()
    expensive_item_name = None
    for idx in range(len(build_items_list)):
        if build_info.get_cost(build_items_list[idx]) <= cookies + cps * time_left:
            if expensive_item_name == None:
                expensive_item_name = build_items_list[idx]
            else:
                if build_info.get_cost(build_items_list[idx]) > build_info.get_cost(expensive_item_name):
                    expensive_item_name = build_items_list[idx]
    return expensive_item_name