Detailed Instructions: In this task, you are given a conversation between a flight agent and the customer. You are given 4 options and you need to select the goal of the conversation. It is provided as part of customer's context, which has to be one of the following: `book`: Make a new reservation, `cancel`: Cancel an existing reservation, `no_flight`: No flight found for the customer's preference, `no_reservation`: No reservation / No change / No cancellation was made in the conversation, mostly enquiring details
Q: customer: Hello. 
 agent: Hello, how may I help you today? 
 customer: Please help me to book a flight ticket from DEN to ATL. 
 agent: Sure, may I know your name please? 
 customer: Melissa Green. 
 agent: May I know your class preference please? 
 customer: I am happy with any class. 
 agent: May I know your preferable time for journey? 
 customer: I am comfortable with any time. 
 agent: May I know your connection limit please? 
 customer: I need a single connecting flight. 
 agent: May I know your travelling dates please? 
 customer: My travel dates are from Feb, 28 to Mar, 01. 
 agent: There is a direct flight of fare 100 with economy class in Frontier airline, shall I proceed for booking? 
 customer: Please proceed. 
 agent: Your ticket has been confirmed with flight number 1015. 
 customer: Thank you for booking. 
 agent: You are welcome.Thank you for reaching us.
A:
book