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, I am George Baker. 
 agent: Hello, how can I aid you? 
 customer: I would like to attend a meeting with my client at Washington, IAD. Can you please help me in booking on 12/14 and 12/16? 
 agent: Sure, may I know your source airport? 
 customer: My source point is Denver, DEN. 
 agent: Let me know your connection limit. 
 customer: I need a connected flight. 
 agent: Sorry, no flights found with your given dates. 
 customer: Ok, no problem. Thank you. 
 agent: Thank you for choosing us.
no_flight