Detailed 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
Q: customer: Hi, I am William Collins. 
 agent: Hello, how may I serve you today? 
 customer: Me and my friend's were planning to visit rockridge ice cream & gelato tour which is in Oakland. Can you please assist me in booking a flight ticket with fare 500? 
 agent: Sure, we are mirthful to help you. Can you please let me know your journey dates? 
 customer: My departure date is 08/17 and arrival date is 08/19. 
 agent: Kindly assign your source and destination points? 
 customer: My source code is TX-AUS and destination code is CA-OAK. 
 agent: Please wait for a while. 
 customer: Sure. 
 agent: Sorry we did not find any flights matching your criteria. 
 customer: Ok, no worries at all. Thank you. 
 agent: Thank you for reaching us. Have a good day.
A:
no_flight