One day, in an English class, the students are having their lessons. Their teacher, a young woman is very happy. She sings some nice songs with them and then she goes to the blackboard and writes "SMILES" on it. "This is the longest（最长）word in English," she says to the class. A girl stands up and says, "It has only six letters. How can it be the longest word in English?" The teacher smiles and says, "Oh, look! There is a mile (英里) between the first letter and the last one."