Exam Shopping

data_list = input().split(' ')

stock_dict = {}

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(' ')
while data_list[0] == "buy":

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

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

    else:
        print(f"{product} doesn't exist")

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

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