Mary likes to invent things. She creates a new language and teaches it to her friend, Jean. Mary and Jean like to talk to each other in their own language because they think no one understands them and it is funny. When they go shopping, they say things like: "Look! He is fat." "This CD is awful." "I want to eat free hamburgers." A clerk comes but he can't understand what they say. He asked them: "May I help you?" Mary and Jean just laugh. What fun it is to create something new. According to the passage, creating something new is   _  .
boring interesting hard easy