Instructions: 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
Input: customer: Hi. 
 agent: Hello. 
 customer: Nancy Evans here. 
 agent: How can I aid you today? 
 customer: I am planning to go to Boston to attend a business meeting, can you please help me to book a ticket from OAK to BOS? 
 agent: Sure, can you please share your travel details? 
 customer: My preferable dates of trip are from 03/05 to 03/07. 
 agent: Wait for a moment. Sorry to say that there is no flight found. 
 customer: Ok, take your time. No problem, thank you so much. 
 agent: Thank you for contacting us.
Output:
no_flight