One day, a policeman was talking a thief (小偷) to the city. On the way, they saw a shop. The thief said, "Let me go into the shop to buy some bread. We can eat it on the train." The policeman agreed. The thief went into the shop and ran away from the back door. When the policeman knew that, he began to look for the thief everywhere. At last the policeman caught (抓住) the thief. They walked to the city. On the way, they came to the same shop. The thief wanted to buy some bread again. "Oh, no," said the policeman. "You did that before. So this time I'll go into the shop and buy some bread. You must wait here for me."