Exam Shopping

data_list = input().split(' ')

stock_dict = {}

if data_list[0] == "stock":
    while data_list[0] != "shopping":

        product = data_list[1]
        quantity = int(data_list[2])

        if product in stock_dict:
            stock_dict[product] += quantity
        else:
            stock_dict[product] = quantity

        data_list = list(input().split(' '))

    data_list = input().split(' ')
    if data_list[0] == "buy":
        while data_list[0] == "buy":

            product = data_list[1]
            quantity = int(data_list[2])

            if product in stock_dict:
                if stock_dict[product] >= quantity:
                    stock_dict[product] -= quantity
                elif 0 < stock_dict[product] < quantity:
                    quantity = 0
                    break
                else:
                    print(f"{product} out of stock")

            elif product not in stock_dict:
                print(f"{product} doesn't exist")

            data_list = list(input().split(' '))

if data_list[0] == "exam":
    for key, value in stock_dict.items():
        if value > 0:
            print(f"{key} -> {value}")