How do I create a loop that will continuously delete letters from the string that are input by the user without using a function?

Create a program that first inputs a string. Then, create a loop that will continuously delete letters from the string that are input by the user. Be sure that the first instance of the letter is deleted... not all instances of the letter. Continue this loop until the user enters “stop” or the string no longer has letters. Be sure that you are looping over all letters of the string (do not use built in functions such as replace).