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: Hi. 
 agent: Hello, how may I help yo today? 
 customer: Stephen Harris here. Please help me out in booking the ticket from MSP to EWR. 
 agent: Sure, can you please mention with your dates of journey? 
 customer: My trip dates will be Mar 27 to Mar 29. 
 agent: Ok, may I know your airline preference please? 
 customer: No. 
 agent: May I know your class preference please? 
 customer: Business class. 
 agent: Please wait for a mean while. 
 customer: Ok. 
 agent: Sorry Stephen, there is no flight found as per your travelling details. 
 customer: That's ok, thank you. 
 agent: You are welcome.
no_flight