To make telephone numbers easier to remember, some companies use letters to show their t...

To make telephone numbers easier to remember, some companies use letters to show their telephone number. For example, using letters, the telephone number , which uses eight letters. Write a program that prompts the user to enter a telephone number expressed in letters and outputs the corresponding telephone number in digits. If the user enters more than seven letters, then process only the first seven letters. Also output the – (hyphen) after the third digit. Allow the user to use both uppercase and lowercase letters as well as spaces between words. Moreover, your program should process as many telephone numbers as the user wants.