Not very sure how to start this program, please help.

Each student will write a C++ program. This program will manage a list of usernames in a computer system. The list of usernames will contain the username as the key field and the First and Last Name as the value field. The following is an example of what the key field will look like, "Smithb": :"Bob Smith" Specific features of the program The program will allow users to enter a First name and then a Last name. This data will be placed into an array of username : name pairs. The user name is constructed from the input. For example, if the user enters Sue Jones The user name would be JonesS For Thomas Re, The username will be ret Lab Challenge: There needs to be a function that will sort the list of usernames alphabetically by the first letter of the username. There will be no duplicates in this list