Given the task definition and input, reply with output. 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

customer: Hello. 
 agent: Hello, how can I help you? 
 customer: I am planning to travel from DEN to AUS, can you please help me to book a flight ticket? 
 agent: Sure, please share your travelling dates. 
 customer: Sure, my travelling dates are Dec 24 and Dec 26. 
 agent: Do you need any connection in between the journey? 
 customer: I need a connecting flight. 
 agent: Do you have any other preferences? 
 customer: My class preference is economy. 
 agent: Ok, may I know your name please? 
 customer: My name is Cynthia Taylor. 
 agent: Ok, please stand by. 
 customer: Sure, I will wait for your response. 
 agent: Thank you for waiting, sorry no flights found with your details. 
 customer: No problem, thank you for your information. 
 agent: Thank you for reaching us, have a good day.
no_flight