Once upon a time, a king celebrated his birthday and gave a big party. It was wonderful and many people came to the feast. There was another king who had come from some distance away for the celebration and as a gift, he gave the king a special bed. This bed could fly and could go everywhere but there was a condition: to read the formula that was on a small piece of paper and sleep on the bed. The King was very happy to receive this gift because he loved to travel and could go anywhere. He slept on the bed, read the formula and it flew. One day the king travelled to another place with his flying bed and he was enjoying it very much. During the trip, the piece of paper that contained the formula got lost without him realising it. He arrived well where he wanted to go, but when the time came to go back, he could not fly.