Create a C$++$ file with the name problem$3.$cpp$.$

Write the function bookEndString, which has a string s and an integer r as parameters, permanently modifying the string s$.$ If the first and last letters of the string are the same, then add r copies of that letter to the beginning and ending of the string.$$ Otherwise, add r Z$\text{'}$s to the beginning and ending of the string. The return type for this function is void.

Write the main function that does the following:

Prompt the user for a string containing at least $3$ letters, validating the input until the user enters a string with at least $3$ letters.

Prompt the user for a positive integer, validating the input until the user enters a positive integer.

Call the function bookEndString passing into it the string and the integer.

Print the modified string.