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. 
 agent: Hello. 
 customer: Nancy Green here. 
 agent: How may I help you? 
 customer:  I am planning to book a ticket to attend a music event at IAD. Can you please help me out to book a ticket from PHL? 
 agent: Sure, I will help you. Can I know your travelling dates? 
 customer: Ok, my travelling dates are 03/11 and 03/13. 
 agent: Sorry Green, there are no flight's available based on your traveling dates. 
 customer: No problem. Thank you. 
 agent: Thank you for reaching us.
Output:
no_flight