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 Barbara Jones. 
 agent: Hello, how may I support you today? 
 customer: I want to attend my sister engagement at Detroit, MI - DTW. Can you please book a connected flight? 
 agent: Sure, please share your dates. 
 customer: Sure, my travelling dates are 06/05 and 06/07. 
 agent: Ok, may I know your heading point? 
 customer: I have planned to start from Denver, CO - DEN. 
 agent: Ok, please be on hold. 
 customer: Sure. 
 agent: Thanks for being on hold, no flights were found based on your details. 
 customer: Ok, no issues. Thank you for your help. 
 agent: Thank you for choosing us.
no_flight