17 people wore red shirts, 15 wore watches and 20 played volleyball. Also: Exactly 8 red-shirted people wore watches. Exactly 13 red-shirted people played volleyball. Exactly 12 watch-wearers played volleyball. Exactly 5 people playing volleyball wore both a red shirt and a watch. From this information, the least number of people that could have been at the Fitness Center is what?
