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. 
 customer: I'm Emma Walker. 
 agent: How can I assist you today? 
 customer: I would like to change my reservation which is under my name. Can you please help me with that? 
 agent: Sure, will you please give me a moment? 
 customer: Sure, take your time. 
 agent: Thanks for waiting, your reservation is found. Please mention your airport code. 
 customer: My source airport code is DEN and the destination airport code is PHX. 
 agent: Will you mention your travelling dates please? 
 customer: I would like to take off on 08/17 and return back on 08/19. 
 agent: There is a flight with price 100 and the connections 0 is available. Shall I confirm your ticket? 
 customer: Can you please check with 0 connection? I need a flight with 1 connection. 
 agent: There is no flights available with connections 1. 
 customer: Ok, no issues. Thank you for checking. 
 agent: Welcome, have a great day.
no_flight