Library Management System

You are required to implement a simple library management system. In this system, you can add books, issue books, return books, and check the inventory of a book. The operations will be provided as commands to your program. You should maintain the inventory of books, where each book is identified by an integer book_id and a string book_name. When processing commands:

• ADD: Add a book to the system. If a book with the given book_id already exists, increase its quantity by 1.
• ISSUE: Issue a book if available. This decrements the quantity if the available quantity is more than zero.
• RETURN: Return a book. This increments the quantity if the book exists in the system.
• INVENTORY: Check the current status of a book. The output should be the book_id, book_name (or None if the book is not found), and its quantity.

Internally, you may consider that the operations follow the following formulas:

\(quantity = initial\_quantity + \text{number of ADD operations} - \text{number of ISSUE operations} + \text{number of RETURN operations}\)

Implement your solution to read from standard input and write the results of every INVENTORY query to standard output.

inputFormat

The first line of input contains an integer n which denotes the number of operations. The next n lines each contain one operation in one of the following formats:

• ADD <book_id> <book_name>
• ISSUE <book_id>
• RETURN <book_id>
• INVENTORY <book_id>

All book_id values are integers, and book_name is a single-word string without spaces.

outputFormat

For each INVENTORY command encountered in the input (in the order they appear), output a single line with three values separated by a space:

book_id book_name quantity

If the book is not present in inventory, output None as the book_name and 0 as the quantity.

## sample

10
ADD 1 HarryPotter
ADD 2 LordOfTheRings
ISSUE 1
ISSUE 1
RETURN 1
INVENTORY 1
INVENTORY 2
ADD 2 LordOfTheRings
INVENTORY 2
INVENTORY 3

1 HarryPotter 1
2 LordOfTheRings 1
2 LordOfTheRings 2
3 None 0

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