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 could I aid you? 
 customer: Jonathan Robinson here. Can you please reserve me a flight ticket from OAK to LAS? 
 agent: Sure, kindly mention your planned travel dates? 
 customer: Sure, my planned trip dates are from July 26 to July 28. 
 agent: Let me know your connection limit. 
 customer: I need a connecting flight. 
 agent: Is there any class preference for you? 
 customer: No. 
 agent: Do you need any other requirements? 
 customer: I would like to return in the evening. 
 agent: We are sorry to inform you that there is no flights found with your matching information. 
 customer: Ok, no issues. Thank you for the information. 
 agent: Thank you for choosing us.
no_flight