John is very unfit and decides to work up to doing a push-up.  He trains 5 days a week for them and starts with wall push-ups.  He adds 1 rep a day and once he gets to 15 reps he will start training high elevation push-ups. and then low elevation push-ups, and finally floor push-ups.  How many weeks will it take him to get to floor push-ups?
What is the solution?