Using python generate a program that scrambles the letters of each word on a file of text. The letters of each word need to be scrambled using the process of keeping the first and last letter of a word in their correct positions, then scramble the letters in between. Only words longer than three letters need to be scrambled. Capitalization must be preserved. You only need to deal with punctuation that comes at the beggining or end of a word (period, question mark, exclamation mark, etc.).

You need to greet the user, eplaining the purpose of the program. You need to prompt the user for the name of an existing file. The scrambled text should be printed to the console.