Following Section 4.9, develop a program that reads a string and removes all duplicates. For example, if the input is Mississippi, print Misp. Start small and just print the first letter. Then print the first letter and true if the letter is not duplicated elsewhere, false otherwise. (Look for it in the remaining string, by using the substring and indexOf methods.) Next, do the same for the first two letters, and print out for each letter whether or not they occur in the substring before and after the letter. Try with a string like oops. Extend to all characters in the string. Have a look at the output when the input is Mississippi. Which characters should you not report? At this time, you should have gathered enough experience that you can complete the program.