Issue with saving screen shot each time with same name and attach with email


I am working on taking a screenshot of using the activity and saving it to one of the folder. As i have to run this process with almost 100’s of line data and each time it runs i need a screenshot with the same name all the time, But i failed to do so. It worked well 1st time but 2nd time when it runs I face an Error saying " Save image : Save image failed. Check if the file name is a valid path"

Thank you