6. (check_ssn.cpp) Write a C++ program that prompts the user to enter a Social Security Number in the format ddd-dd-dddd, where d is a digit, and checks the validity of the SSN (The input may contain either digit or dash and conforms to the mentioned format). Here are sample runs: Enter SSN: 232-23-4532 232-23-4532 is valid Enter SSN: 32-123-4532 32-123-4532 is invalid