Your program should include three components selling, buying and managing for the use of sellers, buyers and the Manager, respectively. Provide a menu for a user to enter each component. 

Selling

When a seller has an item to sell, she/he will first check the catalogue to find a suitable category to place the item. Your program should allow the seller to traverse all  available categories level by level from the root to the leaves. Giving the above catalogue as an example, the program will first show the following root category:

Catalogue:

1 Books

2 Movies, Music and Games

3 Home, Garden and Tools

4 Sports & Outdoors

5 Add a new category

6 Add a selling item

7 Quit to main menu
 
If the user chooses Option 1, your program will list the content of subcategory -

Books:
 
Books:
1 Textbooks

2 Audiobooks

3 Magazines

4 Add a new category

5 Add a selling item

6 Quit to main menu
 
If a user chooses a number which points to a selling item, your program should show the information of the item (expect for the information of maximal discounts). If a user chooses "Add a new category", the program should ask for the title of the category and add it into the catalogue. If the user chooses "Add a selling item", the program should ask for the information of the item and add the item into the catalogue under the current level.  

Note that a category can contain either subcategories, selling items or both. For instance, there could be a selling item under Books, which does not belong to any subcategory under this category.