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 Joshua Philips. 
 agent: Hello, how may I support you? 
 customer: I would like to book a flight ticket to Houston, TX - IAH. Can you help me in this? 
 agent: Sure, may I know your source? 
 customer: I want to fly from Houston, TX - HOU. 
 agent: Ok, can I know your travelling dates? 
 customer: My trip dates are from 05/26 to 05/28. 
 agent: Ok, please wait. 
 customer: Sure. 
 agent: Sorry, there are no flights to your destination. 
 customer: It's ok, not a problem. Thank you for your information. 
 agent: Thank you.
no_flight