It is common practice to move a file to an archive folder of some sort after processing it - perhaps adding 'processed date' to the file name in the process.
If you adopt this process, your requirement changes to become: process and move all available files. A FOREACH container will help you do this quite easily.
If you haven't even tried to resolve your issue, please don't expect the hard-working volunteers here to waste their time providing links to answers which you could easily have found yourself.