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, Emily Lee here. 
 agent: Hello Emily, how can I assist you today? 
 customer: Currently, I'm staying in Las Vegas and planning to move in Houston. Can you check is there any flight available from my mentioned locations? 
 agent: Ok, I will check it but can I know your airport codes? 
 customer: Las Vegas airport code is LAS and Houston airport code is HOU. 
 agent: Ok, may I know your travelling dates? 
 customer: My trip dates are from 10/31 to 11/02. 
 agent: Emily, just wait for a while. 
 customer: Ok. 
 agent: Thanks for waiting, there is no flight available on your provided dates because all the flights are already booked. 
 customer: Oh!. It's ok. Thank you. 
 agent: You are most welcome.
no_flight