Please choose the correct ending to complete the given sentence: Computers and Electronics: [header] How to run an ultra marathon [title] Sign up for the race 3 months in advance. [step] You should give yourself at least 3 months to train, and if you've already signed up and paid for the race that's a great motivator to keep training. Find out about ultra-marathons in your area by searching online or by asking other long-distance runners you know.

Ending1: [title] Do long runs for 2 days in a row once a week. [step] Doing long runs on back to back days is important so you get used to the feeling of running on tired legs. Ending2: [substeps] Remember that there are always more than one marathon enthusiasts in the world. No one will know whether or not you intend to race or simply to round off your running days. Ending3: If you are already a veteran through both training in games as well as your time on the track, you can keep that in mind when planning your race. [title] Make sure to purchase a limited amount of space. Ending4: [substeps] Contact the national race federation for a list of registered, professional training agencies in your area. [title] Find the fastest route to the right destination.

Answer format: ending1/ending2/ending3/ending4