There's a familiar pattern that emerges this time of year: Urban flabster joins a gym to get in shape for summer and gets stuck with a one- to two-year membership contract. Said flabster goes to the gym, finds it sweaty and populated by fit, trim exercise buffs. Flabster has increasingly difficult time mustering inspiration for repeat visits and eventually stops going, yet still pays monthly fee. Fortunately, the Rec and Park Department offers a cheap, if unglamorous, alternative. Nine pools throughout the city offer lanes for aquatic exercise at a couple of time slots each day. You pay $3 to swim, and you don't sign any contracts. Showers and lockers are included, but bring your own lock. If you want to make a bigger commitment — yes, that's the same sales pitch the gym used on you last year — you can buy scrip tickets, which give you a dozen swims at a discount of $28. You may not be stunned by the amenities at these antiquated pools, but for three bucks you're getting a great deal.