In Bereishit 42:24 Shimon is taken away from the brothers and put in prison as surety so that the other brothers will bring back Binyamin to prove that they are not spies. The brothers then return to Ya'akov and retell all the events. He refuses to let them go back to Mitzrayim.
In the beginning of perek 43, the famine increases and the sons have eaten the provisions they brought on the previous trip so they have to appeal to Ya'akov to let them go back down. Meanwhile, the whole time, Shimon was "in jail" and they hung around eating.
How long was Shimon stuck in Mitzrayim (I know that rashi on pasuk 24 says Shimon wasn't in prison but I doubt he was free enough to leave)?