Could anyone, please, explain it to me? I can't understand how to program it. I'm filling the "amount of name" for the storage in the shop and for the queue, then, for each human from the queue, I check, firstly, whether the shop has the product the customer needs to buy, and then, if the shop has it, I compare the amounts. But I have a problem in understanding the part where the shop doesn't have enough of the product and the customers switch places. Could anyone explain it to me?