python+ 酒館做活動的問題

題目：
酒館做活動，1塊錢喝一瓶啤酒，2個空瓶可以兌換一瓶啤酒，4個瓶蓋可以兌換一瓶啤酒。如果有15塊錢，最多可以喝多少瓶啤酒？ 寫個程序來計算，輸入n元錢，輸出可以喝多少瓶酒的數量（不允許借用）

total = 0  # 最終喝多少
left_bottle = 0  # 剩餘的瓶子
left_cap = 0  # 剩餘的蓋子


def cal_num(bottle, bottle_gaizi):
    global total, left_bottle, left_cap

    beers = 0

    # 瓶子，蓋 換酒
    jiu_gai, yu_gai = divmod(bottle_gaizi, 4)
    jiu_ping, yu_jiu_ping = divmod(bottle, 2)
    beers += (jiu_ping + jiu_gai)
    total += beers

    bottle_gaizi = yu_gai + beers  # 剩餘的蓋子+ 啤酒
    bottle = yu_jiu_ping + beers  # 剩餘的瓶子+ 啤酒
    if bottle_gaizi // 4 > 0 or bottle // 2 > 0:
        cal_num(bottle, bottle_gaizi)
    else:
        left_bottle = bottle
        left_cap = bottle_gaizi


if __name__ == '__main__':
    money = 15
    total, left_bottle, left_cap = money // 1, money // 1, money // 1

    cal_num(left_bottle, left_cap)
    print(total, left_bottle, left_cap)