You will be given a definition of a task first, then some input of the task.
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: Hi. I am Michael Lee, arranging a surprise party to my dearest friend on the occasion of her birthday. 
 agent: Hello, how may I aid you today? 
 customer: Please book a flight on 03/17 with one connection. 
 agent: Sure, may I know your airport codes? 
 customer: Origin- destination: IAH -LAS. My arrival date is on 03/19. 
 agent: Thanks for waiting, there are no flights found on your given requirements. 
 customer: Thank you. 
 agent: Thank you.
Output:
no_flight