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 have planned to book a flight on June 14th, so please help me in booking a flight. 
 agent: Sure, may I know your airport codes please? 
 customer: My airport codes are LAS - BOS. 
 agent: Your return journey date please? 
 customer: I intend to return on 16th June. 
 agent: Do you have any specifications? 
 customer: I would like to depart in morning time. 
 agent: Any thing else? 
 customer: I prefer an economy class. 
 agent: May I know your name please? 
 customer: Sure, my name is Daniel Moore. 
 agent: I am sorry no flights found your route. 
 customer: No worries, thank you. 
 agent: Thank you for choosing us.
no_flight