As producing a series involves high expenses, production companies seek to shoot the episodes in the shortest time possible. In contrast to practices elsewhere, the first four episodes of Korean series are usually shot in advance, but the rest are shot continuously as the series is being aired. Scripts are not finished in advance, and may change according to viewer feedback and viewership ratings, where popular characters receive increased screen time and plotlines are changed to match audience expectations. These changes may occur a few hours before daily shooting, and the crew might receive only a few ready pages. The production usually works with three camera crews, who work in a rotating manner to speed up filming. Because of unregulated script changes and tight shooting schedules, actors are almost continuously on standby, and have no time to leave the set or sleep properly. The Korean media have a separate word to describe irregular, short sleeps that actors resort to, in often uncomfortable positions, or within the set: "jjok-jam" (쪽잠), or "side-sleeping". Dramas usually air two episodes a week, one after the other, with the following episodes having to be shot within the intervening five days. Some Korean actors have admitted to receiving IV therapy during filming, due to extreme schedules and exhaustion. Nonetheless the live-shoot model remains widely used since the production team can react to real time audience feedback.